Hitsuji is a spoiled and cute little brother who takes a lot of care. Coupled with Aimi's caring nature, she has continued to take care of everyone since she was a child, even now that she has entered the workforce. However, he is not her real brother, but a younger boy who is her childhood friend. She's worried about him, can't leave him alone when he begs for her, and even starts living with him, but Hitsuji is just like a younger brother to her and not a love interest! In fact, Aimi recently got married and found a good man. But when Hitsuji found out about it, suddenly...!?
あのかわいい羊はどこへいったの…？

手のかかる甘えん坊でかわいい弟・羊。愛深の面倒見のよさもあいまって、小さい頃から社会人になった今もずっと身の回りのお世話をしている。といっても実の弟ではなく、羊は幼なじみの年下男子。心配だしおねだりされると放っとけない、同棲だって始めちゃう勢いだけど、羊はあくまで弟みたいな存在で恋愛対象ではない！事実最近、愛深は婚活してイイ人もできた。でもそれを知った羊が突然――!?