This article is incomplete. Please feel free to edit this article to add missing information and complete it. Specifically, it needs the Japanese release date.
Everything I've said to get you here was a lie. There was never any mission to observe Titans.
Coupling (カップリングKappuringu?) is the 5th chapter of the 2nd volume and the 13th chapter overall of the Attack on Titan: Junior High manga, written and illustrated by Saki Nakagawa.
A dance exhibition is set to occur soon and the students must have partners for the event. Annie tries to ask Eren to pair up with her, but finds herself thwarted by Mikasa at every turn. Later on, Eren reveals he will be pairing up with Armin.
Summary
A dance is announced in the coming weeks at the school. Annie looks at a printout when Krista calls her over. Hearing that Annie is about to head over to Class 4, Krista believes she is going to ask one of them (presumably Eren) to the dance; Annie tells her to keep it a secret. Krista agrees but then immediately tells Ymir, much to Annie's anger.
Heading over, Annie spots Eren, Mikasa and Armin inside. Going in, Annie is immediately stopped by Mikasa, who bluntly asks what she is doing there. Annie tells her that she wishes to discuss something with Eren, but is refused entry. During this, Eren and Armin look on with Armin insisting Eren do something. Annie and Mikasa nearly come to blows when Eren finally goes to see what is going on. Unable to ask Eren to go to the dance with Mikasa glaring at her, Annie spots Hitch and Marlowe outside and uses them as a distraction; she informs Eren that they wish to have Eren observe Titan activities. Eren immediately jumps at the chance and accepts the offer. Mikasa volunteers as well, but Annie refuses stating that only those approved by the student council are allowed to. After telling Eren where to meet outside, Annie walks out realizing that she came up with such a grandiose lie to cover it up.
Soon, Eren arrives in protective gear asking where the Titans are. Annie is about to reveal the truth when Eren spots a Titan nearby and runs over to confront it. Annie reminds him that his "duty" is to observe them. This happens several more times until Annie reveals it was all a sham and calls him a dork for obsessing over Titans. She reveals that she needed an excuse to get Eren away from Mikasa and asks him to pair up with her to the dance. Surprised by this, Eren reluctantly says no. Mikasa, who had been shadowing them the whole time, immediately appears and believes Eren was thinking of pairing up with her; both of them are shocked when Eren reveals he is going with Armin. They both ask Eren to reconsider but Eren reveals that Armin came to him and, knowing Armin wanted to go with someone he trusted, Eren agreed to the request. Knowing there will most likely be other opportunities, Eren suggests Annie and Mikasa pair up together; both of them flatly refuse.