Yasuichi Oshima, born March 24, 1954, in Kyoto, is a Japanese manga artist with a career spanning from the early 1970s to the present day. He made his professional debut in 1971 with the short story Seishun no Tsuchi, which was published in Weekly Shonen Magazine after winning a新人漫画賞 (rookie manga award). Before his debut, he worked as an assistant to the manga artist Kiyoshi Numata.

Oshima is best known as the original creator of the manga Bats & Terry, which was serialized in Kodansha's Weekly Shonen Magazine from 1982 to 1987. The series, a sports manga, was collected into 24 tankōbon volumes and proved highly successful, earning Oshima the prestigious Kodansha Manga Award for the shōnen category in 1984. This work was adapted into an animated film released in Japan on March 14, 1987, produced by the renowned studio Sunrise. The story of Bats & Terry was also adapted into a side-scrolling action video game for the Family Computer (Nintendo Entertainment System), which was released in July 1987.

Another of his credited original creations is the manga Hai Step Jun, which is notable for being a shōjo manga, a genre aimed at young girls. Serialized in 1985, this work was adapted into a 45-episode anime television series. The show was produced by Toei Animation and broadcast on TV Asahi from March 1985 to January 1986, marking a significant expansion of his work into television animation.

Beyond these two titles, Oshima has maintained a prolific and varied career. His extensive bibliography includes works like Oyako Deka, a drama serialized from 1977 to 1981, which was also adapted into a television drama. He has written historical manga, such as the long-running Kenkaku Shōbai, which began serialization in 2008 and is based on the novels by Shotaro Ikenami, and biographical manga on figures like Sadaharu Oh. His series Tenka Dai Monogatari was adapted into a television drama as well.

A consistent theme across Oshima's body of work is his focus on sports, action, and human drama, primarily within the shōnen and seinen (young adult men) demographics. However, his work on Hai Step Jun demonstrates a versatility that allowed him to create content for the shōjo demographic as well. His artistic identity is that of a professional storyteller who has successfully navigated multiple genres and publishers, including major houses like Kodansha, Shogakukan, and Ichijinsha.

His significance to the manga and anime industry is underscored by his longevity and the Kodansha Manga Award, one of Japan's most respected manga prizes. Furthermore, his legacy extends to his family, as he is the father of manga artists Towa Oshima and Yayoi Mishima, and his wife, Reiko Kawashima, is also a manga artist, making him a central figure in a family of creators.