Love Delation! - SMEE
The protagonist arrives back to this hometown. His new school used to be a girls' school, so the ratio of male students to female students is 1 to 9. "Yes, it's a happy school life!!" On his first day at school, he happily opens a door of the classroom... But there are only male students...
As a matter of fact, all male students are in the same class, and not a single girl there... But don't give up. Once he goes out of the classroom, there will be a paradise... "I'll live a happy school life!"