Here's my guide for the Cliff Ending also known as the Suicide Ending. You will need to collect all instrument parts first to skip time later. Afterwards you take several trips back and forth between the next point where you need to wait and your home cave. This guide assumes you have a basic understanding of the game and mostly functions as a reminder of what to do when. If you have any questions please don't hesitate to contact me.

Instrument

• In the room with the red crystals take the middle door
• Take the right door, the middle door and the left door
• In the map room take the middle door
• Pick up the instrument part
• Start opening the door
• Set a bookmark at the door
• Go back to the map room
• In the map room take the left door
• Take the left door and the upper door
• In the moss cave go downstairs
• Take the hidden path
• Pick up the instrument part
• Go back, downstairs, take the left stairs and go downstairs
• Pick up the instrument part
• Use the home bookmark

Concerto No. 1

• Play the instrument 10 times
• This skips 1 hour and 40 minutes

Spider Friend

• Use the door bookmark
• Go upstairs, climb, push the boulder and climb
• Go left and climb the spider web
• Set a bookmark near the spider
• Go upstairs, left and downstairs
• Visit the spider (destroying the web)
• Use the home bookmark
• Go to the mines
• Wait 5 minutes to break the beam
• Pick up the mattock
• Use the home bookmark

Concerto No. 2

• Read Moby Dick & Zarathustra to skip time
• Play the instrument 55 times
• This skips 9 hours

Mushrooms

• Use the spider bookmark
• Climb the new web
• Go upstairs
• Use the mattock (takes 5 minutes)
• Go downstairs and up-right
• Pick up a green mushroom
• Go upstairs to the little cliff
• Plant the green mushroom in the second closest spot to the cliff
• Plant pink mushroom in the closest spot to the cliff
• Create a mushroom bookmark
• Use the home bookmark

Concerto No. 3

• Play the instrument 70 times
• This skips 11 hours and 30 minutes

The End of Longing

• Use the mushroom bookmark
• Walk to the big cliff
• End the longing

Addendum

You might ask yourself how I can make a guide for a speedrun I have no PB in. Well, I did several attempts and watched multiple attempted and completed runs of other runners. I also played the game casually very extensively. Therefore I would say I am very familiar with this run. The only reason I did not finish a run yet is a bug with the mushrooms. Sometimes the pink mushroom won't grow even if you have skipped enough time. This is a known bug which was confirmed by the developer of the game.