Teisoukannen Gyakuten Gakuen Shuugaku Ryokou

The protagonist, Serizawa Seiro, is an otaku with no friends, and his class standing is pretty low. During the group assignments for the upcoming school trip, he was trying to act cool all alone, only to get stuck in the group led by the nagging class president, and his free time destination was decided as the art museum.

But right after that, he was suddenly hit by dizziness... and ended up transferring to another world.

At first glance, nothing seemed different, but it was a parallel world where gender roles and chastity concepts were reversed! Completely different from yesterday, Serizawa is now treated like a beautiful girl and showered with attention.

Though confused at first, he soon figures out how to use his new position. “Class President, change our free time destination. You can have sex with me.” “Really!? Sure!” His convenient request granted, and he loses his virginity!

Then, two delinquent girls who witnessed it blackmail him: “Let us have sex with you, or we'll tell everyone.” He actually takes the opportunity to reverse-rape them!?

Free time leads to love hotels, returning to the inn means a threesome with the female teacher, and the innkeeper and her daughter offer a mother-daughter duo... the school trip is drenched in eroticism!?

[From official site]