What you'll need: letter-making materials (the cuter the better), and friends (preferably one of them is enveloped in zetsubou.)
Senpai: you do nothing but exist. Hopefully you have a mailbox of some kind. You're seemingly ordinary but all the kawaii kouhais think you're pretty kakui. Your sad or depressed. Maybe you lost your job or your Senpai turned you down. Either way you have a platoon of deres lined up to cheer you up. So Sit back, exist, and enjoy some sweet love letter action.
Kouhais: There's several kind of kouhais. (See below). All of you are absolutely enthralled with Senpai. You want nothing more for him to recognize the unrequited love you send him and cheer him up when he's in despair.
This is a love letter making game. Whoever last wrote a handwritten letter gets to be the Senpai first. The rest then pick a kouhai and write their love letter to Senpai. When all letters arrive, the previous Senpai chooses the next one. This can continue for as long as you like! There is no win scenario or anything like that. The only real rule is that all letters must be written in the style of the kouhai the player chose.
Types of kouhai:
If you want to be random about it roll a d8...baka.