はず expresses the expectation that something should or is sure to take place. It follows a verb or adjective and is often followed by だ.
はず is followed by なのに when things don’t turn out as expected. Variations of this are なんだけど, なのだが, and なのですが.
- How to use はず ( = hazu) (maggiesensei.com)
- Using 「はず」 to describe an expectation (www.guidetojapanese.org)
- Kamiya, Taeko. “Expressing Conjecture and Hearsay, and Quoting People.” Japanese Sentence Patterns for Effective Communication, Kodansha, 2005, p. 223
- Makino, Seiichi and Michio Tsutsui. “Main Entries.” A Dictionary of Basic Japanese Grammar, The Japan Times Ltd., 1989, pp. 133–135