He made his debut in 1984 in Fresh Jump magazine with It's late, the pilot for Rokudenashi Blues. This story received the Tezuka Award of Excellence from publisher Shueisha.

After high school, he became assistant to Tetsuo HARA (Hokuto no Ken)

and at the same time published several short stories in JUMP magazine's special issues.

In 1987, he began his first series, Bachi Atari Rock.

In 1988, he began publishing the Rokudenashi Blues series in Weekly Shônen Jump. He captivates his readers with a passionate, lively narrative, a wide variety of characters and excellent pencilling. As a result, the series became a long-seller, publishing for eight years.

As soon as his hit was over, Morita turned his attention to baseball with another successful work in Jump, Rookies (24 vol.) which, although it didn't achieve similar fame, was adored and probably more accomplished in terms of both script and graphics. At the end of Rookies in 2003, Morita was 37 years old.

He was tired of the weekly rhythm, frustrated by the limits of shônen, dreaming of something else, and still under exclusive contract with Shûeisha, who asked him to stay wisely within Jump, doing shônen.