noun
understanding person; supporter
Refers to someone who understands and supports another person, their situation, or their views. Often used for a sympathetic ally or advocate.
彼は私の数少ない理解者の一人だ。
He is one of my few understanding supporters.
新しい政策には理解者が少ない。
There are few people who understand and support the new policy.
味方 is an 'ally' or 'person on one's side', often in a conflict or competition; 理解者 is about emotional or intellectual understanding.
Compound of 理解 (understanding) and 者 (person).