Koganei Kyoudai no Kyuusoku

Older brother Arata, an otaku, and younger sister Hana, a gal, live together in the suburbs. Arata is taking time off of work due to mental illness, and feels guilty staying in his room all day doing nothing. Hana keeps telling him it's okay to do nothing, but also takes him places. Sunbathing, nighttime strolls, the beauty parlor... An unexpected summer break has arrived for the two siblings!

(Source: Futabasha, translated)