Hana, Kiyoshi, Chiyo is probably one of my favs atm. Although it doesn't 100% present itself to be a 愛 triangle. I like how Kiyoshi SPOILER: is sorta going for the unexpected route. Some might think he'd gravitate もっと見る towards the goody goody girl in the end. Which, before Hana came into the picture, he did. But the way things are going now ..who knows.
