In high school, Chiaki and Kazuma fell in love with each other and continued their relationship into adulthood. Despite discussions about advancing their romance, their childhood friend Tomoe interrupts them. Tomoe surprises them with news of her pregnancy and not knowing the father's identity. Aware of Tomoe's free-spirited personality, Chiaki and Kazuma willingly provide emotional support throughout her pregnancy. Upon the birth of Tomoe's baby, they are thrilled to see their friend transition into motherhood. However, their happiness doesn't last as Tomoe approaches them later with a unique request. With travel plans abroad, Tomoe entrusts her daughter, Ayumi, to Chiaki and Kazuma's care as a foster child. As they learn how to be parents, the duo faces numerous challenges where they need to bolster each other up.
