In Exchange for the Strongest Power, I Became a Girl

B-Rank adventurer Rain(♂) had the good luck of finding an Ancient Class item in a dungeon he snuck into. If he sells it, he can have a comfortable retired life! But the joy was brief because due to the item's effects: Rain obtained power equal to that of an S-Rank adventurer and a "Girl's Body"! Furthermore, before he even gets the chance to feel depressed, a certain incident leads to Rain(♀) being invited to [Crimson Heaven], a party with only female members. Will Rain ever be able to return to his original form and take back his peace!?