Yaichi Origuchi's uneventful day is interrupted by a big, burly foreigner who shows up at his front door and begins to hug him. The man introduces himself as Mike Flanagan, and Yaichi quickly discovers that Mike is the widower of Ryouji, his younger twin brother. Since Ryouji left for Canada a decade ago, Yaichi heard nothing about him other than he married a foreigner and passed away the month before.

While Yaichi is apprehensive about the whole situation, his young daughter Kana is absolutely thrilled at the idea of having a gay Canadian uncle. Kana's lack of understanding of Japanese societal views on homosexuality cause Yaichi to reflect on his own preconceived notions. And as Mike continues to stay with the family, Yaichi gradually learns more about his brother-in-law, and he recalls his own past with Ryouji.

Otouto no Otto won the 19th Japan Media Arts Festival Excellence Award in 2015. The French edition of the manga was nominated for Best Comic at the 44th Annual Angoulême International Comics Festival in 2016. In 2018, the series received the Excellence Award at the 47th Japan Cartoonists Association Award. The first volume won the Eisner Award for Best U.S Edition of International Material in the Asia category at the 30th Annual Will Eisner Comic Industry Awards. The manga was published in English as My Brother's Husband by Pantheon Books from May 2, 2017 to September 18, 2018, and in Italian by Panini Comics under the Planet Manga imprint as 2-in-1 omnibus volumes from October 19, 2017 to May 20, 2021. Otouto no Otto was adapted into a Japanese live-action television drama that aired on NHK BS Premium from March 4, 2018 to March 18, 2018.