- Haseo's Japanese voice actor, Takahiro Sakurai , also does the voice of Sieg.
- Haseo stars in a commercial for the game Keroro Gunsou: Meromero Battle Royal Z, where he literally kicks Keroro Gunsou , the mascot, off the screen.
- "Haseo" is an alternate reading of the characters in a Japanese poet's, Matsuo Bashou's, name. His disciple, Kawai Sora, was the inspiration for Sora's name.
- Haseo is 5'8" (174 cm) tall.
- Haseo's arena team is named "Team Haseo".
- Haseo's starter weapons are Spin Gai Gu, Broad Legged, Scythe Shouxiao, and DG-X.
- The weapons Haseo use in the prototype largely remain in the games; namely, scythe he uses (Scythe Hook, can be found in Reminisce) and obviously, the Spin Gai Gu. While the broadsword he uses is not as an equippable weapon, the shape of the sword featured in The World:R2's login screen heavily resembles it.
- The Shopkeeper from .hack//LINK possesses a picture of Haseo in his collection.
- A poll on CyberConnect2's website shows Haseo as the most popular character in .hack//G.U. and .hack//G.U. TRILOGY.
- A notable coincidence is Haseo goes from having a black color scheme to white, while Shino goes from a white color scheme to black.
- Haseo wears the poncho from Form Zero in LINK Twilight Knights.
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