Sousuke wakes up from a nightmare and freaks out when he accidentally gropes Tessa who’s lying next to him. Chidori walks in and yells at Tessa for breaking the rule of not entering Sousuke’s room. Mao finally arrives and helps Chidori keep Tessa in check until the last weekend approaches. Tessa had already arranged plans for a one-night stay at a hot springs inn in Okutama and invited Chidori and her friends, again by Weber’s recommendation. The latter shows up the next day and introduces himself and Mao as students of Tessa’s ‘father’ and managers of the trip. Much to Weber’s dismay, Mao put the boys and girls in separate cars. He uses the opportunity to propose his plan of spying on the girls in the hot spring, and Ono D agrees instantly. Once at the inn Mao suggests they head to the spring before dinner. Chidori suspects that Weber may be up to something, and the latter happens to be listening in on their conversation. He and the boys head out to execute their plan despite Shinji’s hesitation. Sousuke stays behind and gives a cryptic remark about how they should enjoy the bath normally. While the girls are bathing, the boys are listening in on them and Shinji gets an explosive nosebleed with Weber not far behind. Weber attempts to drill a whole through the wall separating them and inserting an optic cable. However, he’s stopped by a metal plate which appears to be of military grade. He decides to raise the cable over the wall but a hidden sentry gun shoots it.
During dinner, the girls announce that they’ll go into the spring again and Weber and the boys decide to change their tactics. Weber plans to peek on the girls using the night scopes on his rifles. As they take off, Sousuke gives Weber the same cryptic warning again. As they climb the mountain, Weber discovers a trap and tells the boys to stop. Shinji panics and backs away, then realizes that he stepped on a landmine. Weber starts to realize that Sousuke is behind all the traps and tries to free Shinji. Shinji however sneezes and sets off the mine, which explodes in a non-lethal blast. Shinji and Ono D are ready to quit but Weber riles them up with a speech. The new plan is for Shinji and Ono D to distract the sentry guns while Weber snipes them, then they’ll have a clear run up the slope to the spring the girls are in. They start running and Weber takes out the guns. Ono D steps on a mine and Weber runs down to save him, but a sentry gun singes his ass. Weber tells Shinji to go on alone, and the latter picks up Weber’s rifle and runs off. Shinji shoots out all the sentry guns while dodging their fire. He jumps into the pool and runs face first into Sousuke’s crotch. Sousuke tells him that the male and female pools switch locations after 10 pm. Back home, the class bids Tessa farewell with a bouquet of flowers and a plaque with their signatures on it. Tessa returns and resumes her duties on the Tuatha de Danaan, vowing to protect all her friends. Chidori helps Sousuke get the safe house back to the way it was. She asks Sousuke if he’s relieved, and admits she’s sad that Tessa left.
Full Metal Panic was bound to have a super fanservice-y hot springs episode, and here it is. Highlights include Sousuke’s nightmare from the beginning and the humorous parody of Gundam SEED’s SEED mode which Shinji enters when he ran up the mountain. Weber and the boy’s little misadventure would have been more hilarious if Weber wasn’t taking himself so seriously, and that scene at the end probably set off yaoi fans across the world typing fanfics like mad. At least Sousuke got a much needed break when he’s not stuck between Tessa and Chidori competing for his attention. Interesting to note is that in this short arc both Tessa and Weber absentmindedly mentioned what their true occupations are but nobody seems to notice.