nightmare-slain
I know you can do it man.
Use Angel for the healing skill.
Have someone with Tarunda, keep that Hydra attack down. If not possible, try Rakunda so at least the fight lasts less time.
If you can't get Aitvaras, Daemon should do the trick to block the fire attack. Whenever you block an attack the enemy losses two press turns, so if the Hydra starts with Fire breath and your Daemon blocks it, it'll lose the rest of it's turns.
Use a dark dampener whenever the Hydra starts gathering magatsuhi. That, again, will make it lose it's press turns.
Whenever possible use the Omagatoki: Critical to fuck up the Hydra. Use Aramasa if your Nahobino is STR based, or Bufu if MAG based.