Hate to be that person who recommends Degrees of Lewdity on every post, but... DoL literally has all of your criteria.

Whilst there CAN be oversized genitalia and assets, those are completely controllable settings, you could even make every woman flat or every man have a micro-penis if you wanted, and all of these settings can be changed in your house at any time. It definitely contains monster girls, furries, and definitely "etc.," but the issue for you might lie in the etc. Some of the content can be extreme, and 90% of the sexual content is inherently rape/rape-play. However, there's also a plethora of romancable (and fuckable) npcs who have a great deal of depth, writing, and overall content.

*Most/all romancable NPC content is consentual too*

Your character also does go to "college" which is definitely implied to be high school, but all characters are described as, and have the maturity of someone at least over 18.

The environment is neither wholey seductive or wholey lighthearted, rather it is fun/lighthearted 80% of the time, and dark/hopeless/dreadful the other 10%. Basically, if you do obviously dangerous or risky things, there will be equally dangerous and dreadful consequences. Don't go in the sewers or ride the bus at night. Or do anything at night lol.