They don't have much confidence in each other and especially with Frisk, although he doesn't show it, he has always been cheerful and an energetic person, in addition to being trained in the royal guard, he has been in situations where he showed seriousness when attacking .  he always has a negative personality and in some cases I even get angry for wanting to have his world back.  And others an evil smile, although when he met Ink, he felt scared.