Soul Beast Union

These two volumes are perhaps the most controversial work Ooishi Naho has done in her entire career. The plot presents a parallel story in which Goku and Vegeta end up being a homosexual couple. While the premise is intriguing, the scenes are forced into yaoi as quickly as possible. It's worth noting that the yaoi scenes are extremely explicit and barely censored, so this manga can be classified as an 18+ doujinshi.

Multi-volume dramatic Goku/Vegeta doujinshi