Well, there's many reasons why people ship Nico and Maki. In the manga, there's details on the story that are a bit different in the anime. Nico, for example, she's a bit more mature and she's close to Maki. In the game, there's a chapter where they are interacting pretty close, Maki shares some thing with Nico and Nico tries to help her. In the anime, there is actually Nico and Maki moments going on like on episode two with them sharing the potato. There are still many more reasons at why they ship them, but I don't want to ramble on.
