A climactic scene towards the end of Sodachi Lost, Owarimonogatari volume 1.
Sodachi has asked Araragi and Hanekawa to find out what happened to her missing mother, and the two of them are sitting on a bench outside her apartment trying to puzzle out the answer from the clues they have.
Ougi shows up and belittles Hanekawa for her uselessness (she's been bullying her throughout the book, really), and threatens to tell Araragi the answer. Hanekawa says to just give her 10 seconds, she'll figure it out.
Ougi starts counting immediately. Ten. Nine. Eight. Hanekawa takes the first seven seconds or so to dash over to a nearby drinking fountain, wash the dye from her hair, dash back to the bench, throw her head into her hands, and think furiously. Three. Two. One. Ze--
