Cardfight!! Vanguard dj - Just a Little More Girl

The protagonist of this story, Aichi Sendo, is a timid boy in his third year of middle school. He had been living his life looking backward rather than forward, trying not to stand out. However, he had one thing that kept him going - the "Blaster Blade", a card from a card game that was given to him when he was little. That card is the reason why he begins to engage in Card Fights, something that changes his life drastically. The name of the card game is "Vanguard". The game takes place in a different planet called "Cray," and due to a never-before-seen play system, it becomes popular throughout the world. (Source: Wikipedia)

Suddenly Aichi found himself in a woman's body. Exasperated, he collapsed in front of Toshiki and Taishi, and they took him (her?) Toshiki's house so the boys could nurse his body... Kai x Sendou and Miwa x Sendou 3P story.