Fai D. Flourite

Fais introduction is in chapter two of the manga in which he is shown sealing away King Ashura of Celes country at the bottom of a pool. He transforms his creation Chii originally from Chobits into a netlike shield instructing her to alert him if King Ashura should awake. He then uses his magic to transport himself through dimensions to the shop of the SpaceTime Witch Yuuko Ichihara. Out of his travel companions Fais motives for joining the group are the least clear. He was the only one to arrive at Yuukos shop purposefully by use of his own means. His wish was to never return to Celes country but as the price for this would have been too great he travels worlds with the group instead. He fears King Ashuras awakening believing King Ashura will chase him through different worlds. The basis for this fear is as yet unknown. According to CLAMP the correct pronunciation of his name would rhyme with eye so instead of spelling it like Fay as they intended they thought that this would confuse readers. Thus they stuck with the spelling of Fai. Spoiler: In Horitsuba Gakuen he is the chemistry teacher.