Alright... but only a bit !!
SPOILER!! .
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Yamato's first love, was Sohgo.
Yamato's first man was Hyodo-sempai, back in High-school.He will tell Sohgo something about Yamato, he didn't know about. That will shock him, but not in a negative way.
Sohgo knows about it, only because he found it out by coincidence.
He ran in to them, while they where doing "it", in school...
He never had a problem with Yamato's being gay, or with them in general.
Half of Vol.4 is a flashback, of Yamato's and Sohgo's Highschool days.
Sohgos had a Girlfirend, which also was his childhoodfriend, Narumi.
So, that's all for now v.v

I'm still in doubt...
I think Yamato will never get serious with anyone because he love Will so much...
I want Yamato to be happy and be in love again...