Ori no Naka

Jirou Gomi, a 29-year-old virgin, has spent the past nine years nerding out with his work colleagues about anime during lunch and drawing erotic doujinshi at night so he can masturbate. However, one day, this comfort zone of his is thrown into disarray by the introduction of a new colleague, Kuroko Yumezora, a bespectacled beauty with long, dark hair and a massive chest.

It only takes a moment to fall in love, just like how it takes a moment to lose your footing. This is the story of a weak man's sins and sexual fixations.

(Source: Kodansha, translated)