You can absorb Genma to death?

Playing through Onimusha 3 and just got Akos green vest. Didn't know quite what it did exactly do I tried it out. I just absorbed near an enemy noticed what it did, so I kept absorbing the souls from the genma and realized you can kill them with this method lol. How have I never known this!? I knew the trick with the white vest where you spin the right stick to heal quicker. What other tricks are there? Lol