Mashu is the kind of friend that that girl doesn't deserve to have, in all honesty.
At first I thought the author really wanted to focus more in the whole thing between Shio, Gai, and Ran... and the douchiness of Rinda, because Mashu, in some kind of way, is too plain compared to the other 3 guys. But, all in all, even that plainness kinda proves how much of a fresh air he can provide given the love triangle stuff and whatever the hell Rinda is doing with his love life. Mashu seems to be more on the ground than the others.