In like a lamb, out like a lion
(Hajime wa shojo no gotoku nochi wa datto no gotoshi;
“The beginning is like a virgin, after is like a running hare”)
A battle strategy that begins with a show of caution and weakness to get the enemy off-guard, then suddenly follows with strikes of such speed and power as to seem like a completely different force or fighter. Beginning slowly and cautiously like a shy girl and ending with the speed of a fleeing rabbit. In more modern terms, pool sharking. By extension, this phrase may also be used to describe any performance that begins in a lackluster way but then suddenly shows its true strength.
Note that this phrase is not (correctly) used to describe a situation that begins amiably or quietly and later descends into hostility or violence.
We begin, appropriately, with the noun 始め (hajime), “beginning,” followed by the particle は (wa). This marks it as the “topic” of the first half of the phrase while setting up a contrast with the latter half. Next comes the noun 処女 (shojo), “virgin,” linked by the associative particle の (no) to the adjective 如し (gotoshi), in conjunctive form. This points us to the second half of the sentence.
This time, in place of a beginning, we begin with 後 (nochi), “after,” again marked with は to change the topic and finish the contrasting pair. In place of the virgin we get 脱兎 (datto), “an escaping rabbit,” connected by の to 如し in sentence-final form.
This strategy comes to us from none other than Sun Tzu’s The Art of War, (『孫子兵法』) in the chapter on “the Nine Situations” (九地).
(“Gakkari shita na, konkai no karate no kumite no aite wa yosou ijou ni yowakatta. Zutto hajime wa shojo no gotoku nochi wa datto no gotoshi teki na sakusen wo tsukatteru no ka to kasuka ni kitai shiteta no ni, kekkyoku, yowai mama datta. Nanka, kinchou shiteta no ga muda ni natta kanji da na.”)
[“That was disappointing; my sparring partner in karate this time was weaker than I’d expected. I spent the whole time sort of hoping they were pretending to be weak in order to set me up, but in the end they were just not that good. It’s like, it feels like I got all keyed up for nothing.”]