My Girlfriend's a Geek (2006)

Blurb:
Taiga is a college student who’s always scraping by. All he wants is a part-time job and a cute girlfriend. So when he spies a 'help wanted' sign outside an office and a hot girl inside, he takes the job, no questions asked. And everything goes well, prompting him to steel his courage and ask Yuiko, a full-time employee at the office, out on date. And when she asks him if it’s okay that she’s a 'fujoshi,' or comics/cartoon geek, he tells her it’s fine out of sheer excitement. But poor Taiga has no idea of how much trouble he’s just got himself into!

Source: www.anisearch.com/manga/6797