It's true that they don't interact that much, but Makoto's probably the one Haru's closest with. Even apart from the nickname, Haru also is the most worried about Makoto in the sixth palace (without spoiling too much, their personal circumstances are similar in some ways).
Bless Glidesloe for giving us everything Saburouta denies us. Even the hickeys and bite marks are perfect (Yuzu likes to give hickeys, Mei likes to bite). I’d love to read a smutty citrus doujin by Glidesloe