Memai wa Madoi no Tsugai

On the day of the earthquake, Hato Fujinoki cannot go home, leading the owner of the bookstore, Kazumi, to ask him to stay behind. With his legs injured and all, he agrees.

"At a time like this, you could say we're in the same boat," Kazumi says.

Because of this sentence, Hato starts to pay more attention towards Kazumi. A few days later, Hato happens to visit a bar with his colleagues, where Kazumi, an alpha who works there, immediately senses that Hato is an omega. And the truth is...?

(Source: Shinshokan, translated)