1st release of the game is very barebones. Using Illusion characters, environments and animations so not going to be surprised there.
The stats are easy to grind (spend time with her, gifts for love, sleep at 8pm wake up at 11:15pm go to her room and play with her for lewdness) and at some point you will be able to ask her to make love. Already saw pretty much everything there is to be seen.
The story can't be factored in as the Engrish is machine translated so that's out the window.
The only way I can see this progressing is multiple paths to corrupt sister (exhibitionism -> public sex, etc; submissive -> bdsm; dominant -> bdsm with male being sub (not necessarily MC); romance - true love; whoring -> threesome and foursome and/or NTR; possibilities are endless)
This "gem" needs something very special to grow into a precious gem, that's for sure.
