Chapter 31

Mission 31 (: 31) is the thirty-first chapter of the SPY x FAMILY manga, written and illustrated by Tatsuya Endo. It was released on August 10, 2020.

Summary
Fiona Frost reflects on how Loid Forger being with his family has led him to develop inappropriate emotions and become a worse spy. Seeing Twilight become like a knife with a chipped blade makes her heart ache. Still, she finds this new version of him adorable and endearing and still yearns for him. Because of this, she is determined to usurp the wife position from Yor Forger.

At the Forger's apartment, Fiona details their new mission to Loid. She tells him of a man by the name of Cavi Campbell who, after earning a fortune in the energy sector, became a world-renowned art collector. For the mission, they seek to acquire the painting "The Lady In The Sun," worth roughly one million Dalc. The painting was previously owned by the late Colonel Erik Zacharis, who worked in the East's military intelligence division during the war and played a major part in ending it. They believe he was in possession of secrets which could reignite the flames of war in documents known as the Zacharis Dossier. It is rumored to contain information about human experimentation by the East on prisoners of war and massacres committed by the West. It is believed that the painting they are hoping to get holds the key to finding this dossier. They hope to retrieve the dossier before the Eastern government learns of its existence and gets it for themselves. The painting is being kept beneath Campbell's mansion with tight security. Loid asks if Fiona has a plan, and she confirms she does.

In an underground tennis court, a doubles match is finishing up, with many in the crowd complaining about losing the money they wagered. Loid and Fiona show up in disguises with tennis rackets in hand. Loid asks Fiona if this was the best option, and Fiona says she believes it to be the most promising one. While the competitors are usually very skilled, the winner of the tournament gets to take an item of their choice from Campbell's collection. It also gets rid of any risks of having to try and steal the painting.

Loid and Fiona get called to play as “Twain and Nafalia Foney,” the names Fiona registered them under, as well as getting introduced as a married couple. Their opponents are Walson and Bobble, a famous duo that dominated the Grand Slam Circuit a decade ago. Loid tells Fiona that he has not played much tennis, and Fiona tells him he just needs to stay in the corner and out of her way. She believes by showing off her tennis skills she can prove how much of an asset she would be to Operation Strix. They announce the betting odds at 120 to 1.3, with Walson and Bobble being the clear favorite to win. Walson and Bobble announce to Loid and Fiona that they have been working hard towards perfection and will win this match. Loid wishes them a good game, to which they respond that it will be a slaughter.

The game begins with Loid serving, and he immediately slams the ball down onto the far edge of their opponent's court, leaving a burn mark on the ground and slamming into the fence. They earn their first set of points, and Loid continues to earn more points without letting the other team get any until they win the game. Walson and Bobble are shocked at their loss but decide in the next game to aim for Fiona since they have not seen her play yet. Like Loid, she destroys them and wins the game without letting up any points.

Campbell's associates begin to question whether the match was rigged or not, to which one of the other associates responds that, unlike those ordinary opponents, Loid and Fiona will have trouble against his Bolic Brothers. Another associate questions this saying they are just drug addicts, but he tells them that their new drug "Oso-R" is being given a trial run in the next match. This drug leads the Bolic Brothers to transform from skinny, non-muscular men to large men with lots of muscle. Loid, after seeing them, questions whether this was really risk-free and Fiona simply responds by telling him they just need to do their best.