Tenjho Tenge Season 1 Episode 6

(Aya uses the Dragon's Eye to see Souichiro's past)
Makiko: Our family... has brought this burden upon ourselves. You must become evil to kill evil. We're the cursed family... who have been hated by both evil and humans for many generations But Souichiro, you must not hate them. Anger and hatred will disrupt you Ki. With a disrupted Ki, you can't use your full strength!
Souichiro: (Crying) No! I'm going to become stronger and stronger... and kill all those guys that did this to you!
Makiko: To become stronger to hurt others is the same as making them stronger. True strength is the lack of fear of getting hurt to save others. You must take pride in that! The Nagis were a tribe that protected a lot of people in exchange for their own bodies. You might not understand right now... but when you realize the true meaning, a dragon will live in your body; not a demon.