tuck into one's obi

a letter, epistle (written message or note) / (archaic) a utility paper used for various purposes, such as for jotting down notes or for wrapping items

(Kagoshima dialect) a letter, epistle (written message or note)

(formal) Female third-person singular pronoun; she, her, girlfriend

(colloquial) a girlfriend (a female partner in a romantic relationship)

(literary) they (about women or girls)

to hide, to conceal

that which is hidden / that which is protected from outside / (clothing) pocket

obi - the sash worn with a kimono / paper wrapper (on books, CD, etc.)

band, belt