this is a no ending game! you're just supposed to check in on him like a tamagotchi whenever you can ^^ all the endings you can get are bad endings, which you can check out how it goes from this short i attached below.
But you'll learn a lore-ish plot once you get to around 100-200-ish affections if you make him make an impression of "yandere" over and over again.
A thing you can do is water his plant and check in on him everyday to gain affection faster until you unlock the options to do things with him (hug, pat, cook, etc)