The fifth line closes a gap and the classic describes the closing physically. Legge's translation says occasion for repentance disappears, that the subject unites with his relative as readily as biting through a piece of skin, and asks what error there could be in going forward with such help. The image is deliberately unceremonious. Biting through skin is easy, immediate and slightly indelicate, and it is the opposite of the formal approach a ruling line might have been expected to make.
The relative is the second line, strong and central in the lower trigram Dui, and the two are proper correlates, one of only two such pairs in the entire figure. Where the second line met its lord by accident in a side lane, the fifth reaches down to the second with no obstacle in the way at all. The classic is showing one connection from both ends and giving it a different texture at each, which is how it registers that a repaired relation feels quite different depending on who was doing the reaching.
Structurally the line is yielding in an odd place and therefore incorrectly seated, like nearly everything in this hexagram, but it is central and it holds the ruling position of the upper trigram Li. The incorrect seating is why regret was available to it in the first place. The centrality is why the regret goes, and the closing question, what error can there be, is not rhetorical padding. It is the point at which a figure of estrangement stops expecting the worst.