Kangeki (感激 lit. Deep Emotion) is a rare and mysterious Kekkei Genkai. Kangeki users are rarely ever found, and while passed through blood, can appear in any person. This Kekkei Genkai is unknown to most people, and sometimes even users are unaware of what they are using.
Kangeki awakens over time, but extreme situations are shown to shorten the time to full awakening. A person born with Kangeki is normally highly aware of the emotions around them, and the strength of a specific emotion around them is what gradually fully awakens this Kekkei Genkai. This can sometimes be incrediblly stressful for people, and can cause them to break down.
Once fully awakened, the powers of Kangeki vary between people. Their ability's strength and form is based on the emotion that caused Kangeki to awaken in them.
A Kangeki can be given to a person, by taking a blood transfusion from them. The chances of gaining the ability is still slim, but there is a possibility. Those aware of this that have Kangeki normally don't donate blood for this reason.