From Renta!:

High schooler Yamato suffers a serious problem - that is, he can't seem to get it up! Even when his friend lends him an adult video, his nether region is unresponsive. Unable to join in the guys' conversations, he's getting more depressed by the day... Just as he's starting to get desperate, he runs into an old friend, Tsukasa, who also happens to be the first person to teach Yamato how to properly pleasure himself. Could it be Tsukasa who triggered this condition of his...!? One - on - one training sessions between a high school teenager and an older, brother - like figure with incredible technique!