It's completely unconfirmed whether or not guitarist Yuuichi (悠一) [cheSs] and bassist Yuhi (遊緋) [BifrosT.] are the same person.

The personal profile of Yuhi (遊緋) mentions that he was in a band prior to BifrosT. whose OHP address was http://13hp.jp/?id=mchessm, leading me to believe that it was some band named chess. Unfortunately, the OHP link is dead and no other information about the band is given.

This particular cheSs is the only which was active in Tokyo (東京) just prior to the formation of BifrosT.. Given that Yuuichi (悠一) is a somewhat similar name to Yuhi (遊緋), as well as the fact that his personal OHP address at the time was http://14hp.jp/?id=yuh1 (which could be read “yuuichi”), it's plausible that they're the same person.

That being said, this is pure conjecture. The birthdate and blood type of Yuichi (悠一) are AB and 12/27, respectively; those of Yuhi (遊緋) are unknown.