I’d still really recommend the Steins;Gate visual novel, but it’s up to you of course.
I’ve heard Symphonic Rain is cool, maybe check that out?
Also, you should probably list what you’ve already played or seen the anime for to give a better point of reference. But since you said you have Key visual novels under your belt, I’ll assume you mean the non-H ones. If that’s true, you can check out AIR which our based lord Takafumi made an all-ages patch for. Unless you’ve done that already.
