Now this is a conversation topic I like
Koizumi's daily life would be interesting to get into. We've been to Yuki's apartment a couple times, and Mikuru is established to be from the future and thus living alone, but other than the mention above, we know
nothing about Koizumi
Until that mention, I thought we'd have a story sometime where we went to his house and it was completely normal, and his parents were all "We're so happy he has someone coming over, that hasn't happened in three years!" xD
But yeah, Koizumi's so calm and collected he must have stayed with the Organization for at least a little while and learned to be...so shady.