Jesus this is a mess. The relationship chart is gonna look like the Gamers! Love Dodecahedron at this point.
Trying here, but I'm too lazy to make a chart, so it's "in text":
Lemon (normal): likes Sunao, is friends with Natsumi, and didn't know (until then) Suzuka (now he wants her to be a fan)
Lemon (Sunao's soul): treats Sunao/Lemon like a sister, is embarrassed to be with Natsumi (but is still in love), accidentally made Suzuka fall in love with her
Natsumi: fell in love with Sunao (Lemon's soul), is friends with Lemon (in both "forms"), doesn't talk much to Suzuka
Sunao (normal and hard-headed): he likes Natsumi, has past (and unresolved) hurts with Lemon, and is friends with Suzuka.
Sunao (Lemon's soul): he is friends with Natsumi (to the point of being able to make her fall in love with him in this mode), he talks little to Sukuza and is a little afraid of Lemon/Sunao
Suzuka: fell in love with Lemon/Sunao, is friends with Sunao (in both "forms") and doesn't talk to Natsumi much