Since most of my characters in 'Haru and Tsukasa' are in high school, you should expect to see a lot of teenage characters:
Sarah, the only character (as of now) who's in college is 19.
The titular characters, Tsukasa and Haru, as well as Juan, Lila, and Olivia, are 18.
Noemi is 17.
Erica, Andrew, Miri, and Dakota are 16.
Pierre and Evangeline are 15.
There are also a lot of characters who are much older than that:
Ms. Harrison. Haru's world history teacher, is 26.
Haru's mom and dad are both 40 years old.