Remember the sidequest where you collect the 15 shells to get a necklace that you give to Ranger May for a golden feather? That, but with no golden feathers. You simply just start collecting the 15 shells, get the necklace and give it to Ranger May. You are not allowed to pick up any other golden feathers. I'm not good at speedrunning but the I just tried it out now and got a time of around 6m 25s, so I'm sure there are things that can be improved. Hope it sounds fun!