Chiaki and Kazuma are two men who began a gay relationship in high school and have kept their romance alive going into their adult lives. Amidst slow-moving discussions about how to take their relationship to the next level, the pair are suddenly contacted by their childhood friend Tomoe. Their reunion is quite the shock, seeing as Tomoe is pregnant and has no idea who fathered her child.

Familiar with Tomoe's free-spirited nature, Chiaki and Kazuma agree to support her throughout her pregnancy. When her baby is finally born, they are overjoyed to see their whimsical friend behaving responsibly as a mother. However, their relief is short-lived since, one day, Tomoe shows up at their door carrying her daughter and making an unconventional request—she wants the two of them to foster her child.

With Tomoe heading overseas, the adorable baby Ayumi is left in the care of Chiaki and Kazuma. As the two learn to grow into their new role as parents, they are tested to their very limits and must support each other like never before.