Premieres January 12, 2025. Check out the ANN article for additional information. Synopsis for the first season from AniList:
Rentarou Aijou was rejected 100 times in middle school. He visits a shrine and prays for better luck in high school. The God of Love appears and promises that he’ll soon meet 100 people he’s destined to date. But there’s a catch—once destiny introduces someone to him, the two must happily love each other. If they don’t, they’ll die. What will befall Rentarou and his 100 girlfriends in high school?
I think no one really pays attention to fictional age in anime. People tend to enjoy the show.