Very fun and tastefully short hentai game. You have to actually give a little thought to how you train the characters if you want a good ending. If you are careless and just watch all scenes like I did Chika is gonna accidentally fuck Miyuki to sleep or NTR Kaguya (which Idon't fault Miyuki for at all.)
Kaguya is the easiest of the two, relax her at the spa, have her try a couple outfits and teach her a bit and she is ready. Miyuki is harder since he starts out tired and, though you only need to boost his confidence, you have to do so while making sure you don't tire him out or get him completely addicted to Chika.
It's a fun while trying different combinations of actions to get all the endings and it's obvious how to reach each one once you nail the mechanics. Only one a bit more obtuse is the Secret ending since it's quite specific, but that's fine since it's a reward for fully engaging with the game.