I found a bug about segment conversion in upstream. http://code.google.com/p/ibus/issues/detail?id=147
Upstreamed fix: http://github.com/fujiwarat/ibus-anthy/commit/1214c7e531683b7bf73c2c2375230e0c7ad1a559
Integrated. http://koji.fedoraproject.org/koji/taskinfo?taskID=2048089