To avoid looking like she forgot Chiyo's birthday, Sekine is forced to use a "forbidden" psychic skill that causes her to temporarily gain weight so she can sky-write a birthday message. Character Developments
The episode emphasizes her role as the "straight man" of the group, burdened by knowing everyone else's secrets while struggling with her own social standing. 4-nin wa Sorezore Uso wo Tsuku - Episode 3 discussion 4-nin wa Sorezore Uso wo Tsuku Episode 3
When a local street food vendor gives everyone except Sekine an extra takoyaki ball, the other girls feel guilty. This leads to a series of comedic misunderstandings as they try "too hard" to be nice to Sekine, which only makes her feel more excluded. To avoid looking like she forgot Chiyo's birthday,
His internal monologue during the "boob speech" highlights that despite his female disguise, he remains a teenage boy at heart. This leads to a series of comedic misunderstandings
In a misguided attempt to make Sekine feel better by comparison, Rikka nearly uses her alien technology to turn everyone else in the vicinity into "space pigs".
A flashback reveals that the four girls didn't initially bond out of pure friendship. Sekine, using her psychic powers, originally charged fees to help her classmates—including Tsubasa—avoid trouble with teachers.