Ai is a Mayfly

My shadow is a cute, chubby girl! We're inseparable, even in the bath and toilet!? Ai, a beautiful girl shadow who is the opposite gender to Kagerou, appears to take his place! But in the middle of their pleasurable body-swapping ritual, they are interrupted by Ton-chan, who claims to be his girlfriend, and only their lower bodies (or rather, their crotches) are swapped!? What will become of Kagerou, who has become a shadow, and Ai, the beautiful girl whose crotch remains male...?