Katawa Shoujo Forums

Yuko is a potted plant; you know... background scenery. She is there for when Hisao is alone with her so he can talk to her like a gardener talks to his plants. The "approachable young adult who gives advice" plot device is another way you can describe her.

When I get around to writing some fanfiction, I think both Kenji and Yuuko will be my favorite side characters to write for.