Fruits Basket (assuming you've seen/read it)
Fruits Basket was high-school me’s JAM. I think I got up to volume 18 or 19 of the manga but unfortunately I never finished it properly and just read spoilers years later.
Fruits Basket is a very charming slice-of-life with a good simmering slow burn of a plot about becoming better as a person and overcoming abuse. Most of the characters were charming and well-written and you wanted to root for them. My personal favorites were Hana and Uo (THEY WERE THE BEST), and also Kyo and Momiji and Rin. I think as the manga went on it did a good job of deepening Tohru’s character from just “standard all-loving shoujo heroine” and I loved the chapters that went into her mom’s backstory - also was a rare great use of the Dead Mom Trope - though she’s dead at the start of the story, Kyoko’s influence on Tohru and others is still a major part of the plot and she’s more than just the “Ideal Mom” character.
My annoyance at the forced heterosexuality for like EVERYONE at the end aside, I imagine Fruits Basket probably still holds up very well as a primarily high-school-set shoujo manga that would still appeal to a wide audience.