Shizuka is Hachiman's language teacher who also serves as his futures advisor/counselor. She is aware of Hachiman's supposed "problems," and takes steps to ensure he is freed from them, her first move being to force him into joining the Service Club. However, she appears to have some quirks of her own: she is a young smoker, she is very sensitive about her age, and she is often prone to quoting or copying scenes from popular shounen manga. She also never remembers to knock before entering the Service Club's classroom, much to Yukino's chagrin.
(Source: Vistrans)