The monkey was asked by Goda, who lives in a mansion, to unlock the lock of the warehouse that the key could not be found. Paintings, pottery and antiques were stolen from the warehouse. After this, thieves enter the shops in the shopping district in succession, and the monkey infers that the crime was committed by a professional key master based on the situation at the scene. Meanwhile, Monkey, Yamamoto, and Yamada hold a joint party with Minami Nishiyama, an adult who started a part-time job at a fruit shop, and her friend. The monkeys enjoy a joint party with Arasa, who proposes a game with a kiss, but Yamada is informed that a thief has entered the shopping district again. Later, Yamada and the detective come to the Sarumaru key store. The detective tells him that he will arrest the monkey on suspicion of continuous theft of the shopping street.
サルは豪邸に住む合田に頼まれ、鍵が見当たらないという蔵の錠を解錠。蔵からは絵画や陶器、アンティーク品などが盗まれていた。この後、商店街の店に連続して泥棒が入り、サルは現場の状況からプロの鍵師の犯行と推理する。そんな中、サルと山本、山田はフルーツ屋でバイトを始めた大人の色気漂うアラサーの西山みなみ、その友人と合コンを開催。サルらはキスを懸けたゲームを提案する大胆なアラサーとの合コンを満喫するが、その最中に山田は再び商店街に泥棒が入ったという連絡を受ける。後日、山田と刑事が猿丸鍵店にやってくる。刑事は商店街の連続窃盗の容疑としてサルを逮捕すると告げる…。
