Born as the second son of three brothers, Kenta was always seen by his mother Riko as quiet and shy. However... one spring when his older brother moved out for work and his younger brother went off to boarding school, their father left for an overseas assignment leaving just Riko and Kenta living together under the same roof. As the once bustling household grew quieter, Riko began feeling lost and empty. Seeing her distress, Kenta couldn't help but feel regretful that he had never fully appreciated his siblings or realized how much love his mother had given them all. Determined to make up for it now, he decided to shower her with affection and attention - hoping to fill the void in both their lives.

3人兄弟の次男で生まれてきた健二。母親・礼子からすると大人しく引っ込み思案という印象だったのだが…。ある年の春、兄は就職して1人暮らし、弟は寮制の学校に入学。父親は単身赴任と慌ただしく生活が変化して健二と礼子の2人暮らしが始まった。賑やかな家が静かになり礼子は喪失感を感じていて…。そんな母の様子に健二は、兄弟ばかりを気にする悔しさと虚しさを感じ、母親の愛情をその一身に感じようとして…。