I don't remember a lot of details; all I remember is that you're a male protagonist with three love or sexual interests. The first girl you meet is a red-headed classmate that you can have sex with in the school bathroom. The second girl is a teacher at the school who you can help with some plumbing at some point as a quest. The third girl is a sister or stepsister who visits you when you first meet her, and if you want to interact with her, you can take a train to another city. The overworld of the game is 2.5D, and the artwork is 2D. I believe the engine used is Unity, but that's just an educated guess from my memory; all I'm 100% sure of is that it isn't HTLM or RenPY. I've looked for it but couldn't find it. I found it here on f95zone, and I believe it should still be here.