Issei Tsubaki (椿 一成 Tsubaki Issei) only appears in Full Metal Panic? Fumoffu. He is the president of the karate club at Jindai High and Sousuke Sagara's rival who is a skilled martial artist, but he requires thick glasses because of his short-sightedness.
- The name Issei means "one" (一) (is) and "become" (成) (sei).
- Issei's surname Tsubaki means "camellia flower" (椿).
- Issei is sometimes accompanied by three identical karatekas, all black belts.