An Eccentric
Eccentric, Oddball
A strange person is an eccentric. They are also an oddball.
へんじん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
あの変人のクローゼット、見た？
Did you see what's in that weirdo's closet?
変人的なふるまいをしつづける世界記ろくにちょう戦したが、おしくも世界記ろくにはあと十分足りなかった。
I challenged myself to set a new world record for acting like an oddball, but I was ten minutes shy.
あなたの上司はちょっと変人ですが、すぐに馴染めると思いますよ。
Your boss is a little eccentric but I think you’re going to fit right in.