Watsuki's pretty much covered everything there is about this guy in his comments about Takeda Kanryuu. He was learned in military strategies and practised medicine. A homosexual. Not an impressive piece at all - he sucked up to those in power and bullied those beneath him, and often outstepped his boundaries by throwing his weight around. What made him so exceptionally despicable was that he betrayed the Shinsengumi to team up with the Satsuma Ishin Shishis, just because of the benefits and profits. Finally assassinated by Saito.