Ui no Kisetsu

Working at a public office, Haru leads an ordinary life. He lives together with Shuuji, the son of his high school crush and friend, Natsu, who passed away. Shuuji, who is set to move out after he graduates high school, looks just like his father. As they live together, Haru starts to grow feelings toward Shuuji and agonizes over whether he should be spending time with him as his guardian. But then, Shuuji also begins to develop feelings for Haru. Meanwhile, a man who claims to be Haru's lover shows up and tells Shuuji he and Haru are dating. Shuuji runs away from home, confused by the side of Haru he didn't know. With his secret revealed, Haru and Shuuji start to grow apart because of their feelings for one another, and...

(Source: GOT)