Subaru is a teenage neet boy who was shopping in a convenience store, after going out of the door, he finds himself magically transported to a fantasy world. In there, he meets with 2 mysterious twin maid sisters.
The sisters cannot live unless they replenish their “mana”. So he helps them replenish their mana by ejaculating. And every time he does so, he rewinds the time. Thus, he finds himself stuck in this timeline, and unable to meet with his true love: Emi-chan.