I can't tell if this is a character name pun or a typo.
It's a common romanization problem.
Much like interchangeable R and L sounds ("I Like Jerry Beans!" on a screen in an episode of Galaxy Angel), and sometimes-on-sometimes-off extra U's (Gouku/Goku, Gensoukyou/Gensokyo), when people romanize the "tsu" symbol, they sometimes write it as "tu." This is most likely due to the fact that the rest of the "t" section of the katakana are ta, te, chi (sometimes romanized as ti, see Mystia's varying Chin-Chin/Tin-Tin), and to. It happens, and I'm sure no pun was intended.