Who is the character on Suguru's shirt?
It's possible that it may be Yume Kuonji, the pink haired girl from Kimi ga Aruji de Shitsuji ga Ore de, the other visual novel from MinatoSoft, the maker of Majikoi. There's a lot of various character designs and the character on the T-Shirt could just be a stylized version of Yume. It's hard to tell from the screenshot above, but you can see in the other screen shot the ahoge, single strand of pink hair that's part of Yume's design.