Luffy's observation haki lets him see or feel if someone is good or bad, he and Rayliegh talked about it when he was in training.
I only remember the thing about observation haki is that it can tell how many and determine where is your enemy plus the awakening where you can see a glimpse of future. I didn't know it can tell the character and personality of someone or did I slipped something this important somewhere
It's this one ( http://www.mangago.zone/read-manga/one_piece/mr/m_chapter-894/pg-4/) and the next page after that.
Ohhh, thanks (๑•ㅂ•)و✧
I don't really think luffy is idiot for trusting way to lightly. Is it just me or I see luffy as someone who can tell if one is good or not, or he is just going along with his instinct lol