What makes a true friend is their brutal honesty towards the other.
"Faithful are the wounds of a friend; but the kisses of an enemy are deceitful."What is a true friend? It can be someone who does exciting activities with others. It can be someone who hangs with you at the bar and drink some beer. It's someone who will stick by your side even when others don't respect you or even stand up for you against that nasty ol' bully. It can be those who always tell the truth, whether they like it or not, which is this trope. What is meant by true friends telling the truth? Well, when moral argument falls into deaf ears, this friend isn't someone who isn't always going to suck up to The Hero. If the hero has flaws (especially a moral flaw), his friend will point it out with full-on bluntness, making sure that the hero improves his behavior. If the hero is falling out of line, his friend will verbally chastise him, making sure the hero goes to the right direction. He may be someone who doesn't share the hero's interests or opinions, and would inform him about this, although they wouldn't mind a bit. Despite his honesty, this doesn't mean they can't be friends. This friend truly cares for the hero and wants the absolute best for him. The hero's response to his friend can vary. He may take heed to his hurtful, yet helpful advice and becomes grateful for having a friend like him, although sometimes his gratitude may not be easy, and he may respect his personal opinions and interests. But if he doesn't appreciate his honesty, this will create fierce tension between the two and they may have their friendship to self-destruct. There are two moral lessons regarding this trope. One, if a friend tells you something you don't like, then that means he/she is your real friend. Or two, friends should always be honest with each other no matter what. The polar opposite of False Friend who happens to be a character's enemy pretending to be his friend. The friendship variant of Honest Advisor. Compare Vitriolic Best Buds for friends telling uncomfortable truths out of disdain for each other while still being friends. Compare Big Brother Mentor.
-- Proverbs 27:6, KJV
Examples:Anime & Manga