Hasegawa (長谷川, Hasegawa) is a supporting character in the Sekai-ichi Hatsukoi series. He is novelist Ryouichi Sumi's editor at Marukawa Publishing and he encourages Ritsu Onodera to transfer to the literature department.
Hasegawa has short black hair and brown eyes. He appears to be in his twenties or thirties. When he meets Ritsu at Marukawa, he is wearing a yellow shirt and a purple-blue jacket.
Hasegawa is escorting Ryouichi Sumi out to a taxi when Ritsu Onodera runs into them. Ritsu used to be Sumi's editor, and Sumi introduces them. Sumi informs him that Ritsu is the heir of Onodera Publishing, which Hasegawa appears impressed with but which embarrasses Ritsu. Sumi goes on about how Ritsu was meant to be in literature until his taxi arrives and Hasegawa, Ritsu, and Takano see him off.
Hasegawa later visits Ritsu in the Emerald editing department, bringing him a stack of Sumi's novels to read. He also informs Ritsu that it would be easy to transfer to the literature editing department. This leads Ritsu to later make a choice of whether to stay in the Emerald department or transfer to edit literature as he had originally intended.