it's a shame it wasn't explained so I'll do it:
Page 28, what Second said was "itadakimasu", but probably Sherry had some flowers in the head so what she heard was "ittekimasu" (common phrase when someone is leaving home, like going to work, with the intention of coming back), to which she replied with "itterasshai" ("take care" or "come back safely").
so a very common interaction between a husband and his wife~
(ofcourse, it's generally used between members of the same house, but that was Sherry's intention)