Hello!

If you don't mind, I made a short video guide on how to complete this sidequest quickly.

The reason being I have seen some of you (not mentioning any names) struggle a bit with it, knowing what the triggers are, in randomizers, for example. This can be helpful for people doing 100% runs as well, but I'm sure most of you already should know this, right? After a couple of decades or so playing TWW.
(Well, to be honest I wasn't 100% sure either what the exact triggers were until today, when I finally decided to test it.)

Anyway, here's my humble video:

For future reference, this sidequest can be sped up by quite a bit compared to this video. You only need to take the coloured picture of Linda (you don't need to talk to her), talk to Anton once to clear his first text, show him the picture, and then talk to him again after showing him the picture. They will then be in the Cafe any following day as long as you go there during day time.

You don't ever need to talk to Linda this way.

Do you have evidence this works?
My experience trying was that it was Linda that had all the triggers.
You need to have the Deluxe Pictobox and she will ask you for doing this favor of showing Anton a photo of her, and then when you have, you need to talk to her again to have her say "Maybe he will come, tomorrow...". Without her saying that, they would not show up in the cafe.

I believe I tried your version without it working, but I might be wrong.
Regardless, I don't see the other version being that incredibly much faster, since my video is just going between both of them once each and then for Linda's textbox and then to the cafe. At least for the rando the textboxes are instant, but you'd lose time in e.g. HD since those are slow as molasses.

There hasn't been a new SD 100% speedrun submitted in a while, so a lot of things are outdated, but if you check out any top TWWHD 100% speedrun you will see that they never talk to Linda. If it didn't work for you it's probably because you didn't talk an extra time to Anton after showing him the picture.

This run is a good exemple:
He takes the picture at around 41:08 (video timestamp), never talked to Linda, and leaves. He comes back to Windfall at 2:10:08 and shows the picture to Anton after talking to him, then talks to him an extra time. He enters the Cafe at 4:10:19 for the heart piece.

This works in rando since rando doesn't change those flags.

Yeah I have seen both that run and many other runs of people doing this.

My point with this guide was that once you have gotten the Deluxe Pictobox, this is all you need to do, that is in my guide.
But if you can just take the photo, show it casually to Anton (after at least having talked to him once) and then go to the cafe whenever you like, during daytime, that's all cool.
A few times when others (even pro runners) have tried in the randomizer, Linda and Anton didn't show up in the cafe.

All in all, the steps I do in my video are very few and it's quick.
Also, when you do a rando there's no reason and maybe it's not even possible to delay a side quest like you can in a hundo run, because then you do it to save time, while in a rando you may have have a reason to complete this quest asap to be able to progress. And that was also one of my goals making this guide. If it was all crystal clear and easy as pie to do (understand) this, I wouldn't have bothered posting here.

Yeah, I still think this is a really good guide that will make anyone able to obtain the heart piece. However, this is a speedrunning forum so we should be more strict when talking about what the bare minimum is for that heart piece.

This game in particular has had an history of having very bad documentation (the IGN guide itself says that you can obtain the magic armor from the Windfall auctions which is completely wrong), so I don't want slow things to be used as a reference for future routers, glitch-hunters and speedrunners. It has happened several times that someone figured out something had actually never been necessary to progress the story. Every single time it has caused a major reroute, saving way too much time for what the novelty really was.

I know I was a bit aggressive and I must apology. Your video is still a very good piece of information, and an actual piece of correct documentation, thing that is not easy to find for this game, thank you very much for that!

I want to give this thread an update, as "further investigation" about this side quest has shown two things.
A. azer was wrong about what it takes for completing this side quest. You can't compare HD and SD. It's not the same games and they use different flags and have some removed from HD since the whole thing about the PictoBox/Deluxe PictoBox was changed and things were made easier.
B. My guide and video was incomplete, since I had done a lot more than just collected the PictoBox and its upgrade before doing the guide.

Thanks to the randomizer allowing to choose starting items, I have done some more testing and now I am certain you have to do the Lenzo's assistant side quest first. Not more and not less.
Therefor I made a new video guide:

This was done on the latest version of the randomizer.

It might also help for everyone interested to post the video description (steps) here for easy access:
Basically, to get the reward for getting the two "lovebirds" to go out on a date, you need to:
Have the PictoBox,
Do everything needed to become "Lenzo's assistant" (because believe it or not, Lenzo has an important part in this, as he is Linda's "fortune teller" and also knows about Anton and Linda and their fancy for each other),
Have a Deluxe PictoBox (I am starting with one as an only item in my inventory here),
Talk to Linda and help her take a color photo of her,
Show it to Anton in a way so that he looks "excited" and wants to go out for a coffee with Linda.
You also need to play Song of Passing after Lenzo's lengthy quest, to trigger Linda noticing you are a "pictographer" so she can entrust you. And, finally, play Song of Passing after Anton has decided to go out with her for a coffee (at the café) - because they won't just "teleport" to the café immediately. (If you were to speak to Linda once again, she would quietly say "maybe he will come... tomorrow".)

While I can't say I'm 100% sure you have to play it out exactly like in this video, and you could take a more casual photo of Linda to show Anton, this is how you make sure to get the desired result. Also, if Anton is a bit "slow" (like in this video and his amnesic dialog), just talk to him until the right trigger is hit, and/or show him the same pictograph again (i.e.: don't play the Song of Passing or take a new pictograph of Linda).

Nothing else is needed than what's shown in the video, such as e.g. completing a dungeon or receiving some other item(s) or going somewhere and come back.

Except that with further investigation HD and SD are stricly identical. The flags are absolutely identical, there is no doubt about that. The information I was missing (and nobody knew about until a few months ago actually), is that one day need to pass between getting the deluxe pictobox and showing the picture to Anton. Talking to Linda can be skipped and that is done in 100% speedruns.

Having to become lenzo's assistant was always known and assumed since the picture has to be in colour, and you can't get the dx pictobox before becoming his assistant, only in rando is that possible.

So two things. I covered in my guide here that you need to play Song of Passing before taking the color pic of Linda and showing to Anton. I doubt however that's the only trigger, since, like you see in the video, Anton doesn't "want to go on a date" just by showing the photo once to him and then talking to him.
Many times when people get around to doing this quest they have already completed dungeons and other things so that's why the trigger is easier to hit than if you'd get the Deluxe Picto Box very early. I only want to fill in the gaps.

And this guide was always directed to people doing 100% randomizer runs, since the SD/HD 100% routing makes this whole quest a non-issue. Also, I don't consider myself knowledgeable enough to write guides for such routes or people. I wrote this 6 months ago as well, so I don't know why you think I am aiming this guide to hundo runners, and thus why you compare HD/SD and SD randos when the goals are so totally different and the rules and conditions as well.
The fact of the matter is that I have seen lots of rando runs failing to figure out how you get Linda and Anton to appear in the café, so that's why I thought this guide is of big help. Unless everyone has figured this out already. I haven't seen any recent 100% rando runs (since the any% rando runs don't include this side quest) for some time now. Still, my guide should remove all the question marks around this for good and I'm not expecting to see any confusion around this side quest any more. Because simply having been told that all you need to do is play Song of Passing twice or wait to the next day, once you have the DPB and then show Anton the photo could still confuse people if it doesn't work... At the very least I show in this new guide that you can get it all to work with minimal effort or "puzzle" solving.
Maybe we will see during the next 100% rando if things are as crystal clear to the top runners as you want me to believe. (Meaning also if they get the DPB "early" enough.)

Alright, whatever you want to say. Talking to Linda is still absolutely unnecessary and I'll make sure no speedrunner ever does that, in SD hundo, HD hundo or randomizer runs.

"And this guide was always directed to people doing 100% randomizer runs, since the SD/HD 100% routing makes this whole quest a non-issue. Also, I don't consider myself knowledgeable enough to write guides for such routes or people. I wrote this 6 months ago as well, so I don't know why you think I am aiming this guide to hundo runners, and thus why you compare HD/SD and SD randos when the goals are so totally different and the rules and conditions as well." Alright. But why posting it in the speedrun leaderboard page then ? There's Nothing related to randomizer in Here, just SD speedruns...

Most runners probably don't care to check any forum posts on speedrun.com. At least in the communities that I'm a part of (3D Zelda games), the only function of this site that gets any consistent attention is the leaderboard itself. Communication within our communities happens almost solely through discord servers, so if there is a "right" place to post this guide or start a discussion about it, it would probably be in either the Wind Waker Randomizer discord or the general Wind Waker speedrunning discord (so you would have to create an account).

That aside, there definitely has been confusion about the proper triggers for this quest in the past. I personally had trouble with it before, although that's because the specific flags of this quest hardly ever come up within runs that I do, and as such, it was never a priority of mine to try and memorize exactly what they were (as I usually just forgot about it altogether after runs which may have needed it).

Ouch. I had written a lot of text here but got a "405 not allowed".

Either way, hi Gym.
I actually had you in mind when making this guide since I watched all your rando runs, some several times even, since it's good entertainment. Watching you confused about this quest I figured I could help. Plus that I myself was in the dark about the go-about of it.

In short, all that normally is missing for runners is to talk to Anton once before and twice after showing him the pictograph, as seen in my new video (I replaced the old one in my first post with the new one). So three times in total, at the same occasion.

I might have made an unnecessarily big deal out of this and also come to the wrong place doing it, but I hope no one feels like I have been some sort of plague here. I only had the best intention and wanted to help out.
I promise to go to the discord server next time.

Here's to more randos from you gym and a good weekend to everyone. =)

Lastly, to avoid confusion again, the new video is this one: