His works are noted for their extensive detail, elaborate fantasy settings, and for their juxtaposition of elements from Japanese, Balinese, Thai, Tibetan Buddhist,[3] African, and Indian art.
[4] While Hasegawa focused primarily on depictions of muscular male physique, he often incorporated extreme sexual themes in his works, including bondage and sadomasochism.
[3] Hasegawa cited Go Mishima and Tom of Finland among his influences, calling the former "a master illustrator of the male physique" in an obituary written in 1989 for Barazoku.
Beginning in the late 1980s, Hasegawa began making regular trips to Bali and Thailand, resulting in a greater focus on Asian iconography and mythology in his art.
[3] His artwork was initially disposed of by his family, though it was recovered upon their discovery of a note – alongside a portrait of Yukio Mishima painted on a stone – granting ownership of his works to Gallery Naruyama in Tokyo.