My Stepmom's Daughter Is My Ex

Back in middle school, Mizuto Irido and Yume Ayai dated, bonded over books, broke up right before graduation, and then — because life has a sense of humor — their parents got married and made them step-siblings. Now they're living under the same roof, going to the same high school, and pretending none of that relationship stuff ever happened. They even set up a 'sibling rule' where whoever acts like an ex first loses and has to treat the other as the older sibling. It's petty, it's stubborn, and it's honestly pretty entertaining to watch two people who clearly still have feelings for each other try this hard to act like they don't. The dynamic works because both Mizuto and Yume are sharp, a little prideful, and terrible at actually letting go. Their bickering has real texture to it — you can feel the history underneath every loaded comment and awkward silence. The 12-episode TV series from Project No.9 keeps things light with solid comedic timing but isn't afraid to let the romantic tension breathe when it needs to. If you liked the messy relationship dynamics of Domestic na Kanojo but want something way less melodramatic, or if Ore no Imouto scratched a certain itch for complicated sibling-adjacent situations, this one fits that niche well. It's a comedic, romantic slow burn where two exes keep tripping over their own feelings while pretending they're just family now.