Loveless is a very confusing anime and is sadly a victim of an unfinished adaptation of the source material that asks more questions that it is willing to answer. That being said the series has one of my favorite bubbly side characters who is the perfect side line cheer leader for the emotionally stunted Ritsuka.
Yuiko is the complete opposite to Ritsuka and that is why she compliments him and the series so well. Things can get pretty dark and emotionally jarring throughout the series but Yuiko’s bubbly and infectious smile can be a breath of fresh air.