9'ε

9'ε (ナインイプシロン) is a character in DARLING in the FRANXX. He was a Parasite who served in the 9's, a special forces unit that APE directly controls. He was partnered with 9'δ and piloted a FRANXX called 9 Model.

Appearance
Epsilon has purple hair and grey eyes and wears the standard 9’s uniform. Of the four stamens, he is the tallest in stature, as shown in his first appearance with the entire Nines squad in Episode 12.

Personality
Like all the 9’s, Epsilon possesses no emotions and lacks the ability to understand trivial concepts. However, he is deeply loyal to APE and his comrades.

Episode 06: DARLING in the FRANXX
Strangely enough, Epsilon does not appear in the Nines cameo in Episode 6. It's quite worth mentioning that the other three stamens present above the site of the plantation kissing (Alpha, Beta, and Gamma) are the copilots of the triplet stamens.

Episode 12: The Garden Where It All Began
Epsilon makes his first cameo appearance, this time alongside the rest of his squadmates, including Gamma, Delta (his FRANXX partner, shown in Episode 15), and Zeta (along with her two identical counterparts).

Episode 14: Punishment and Confession
Epsilon makes his third cameo appearance, waiting with their leader to welcome back a sorrowful Zero Two to their fold.

Episode 15: The Bird that Shares Wings
Epsilon appears in the Battle of Gran Crevasse, and he is the first stamen of the Nines faction shown to be in the reverse position, as his partner Delta gleefully tells the klaxosaurs, "You're boring. Entertain us more!"

Episode 17: Eden
Epsilon shows up with his squadmates at Mistilteinn as ordered by Papa. He quietly waits for Alpha to tell Squad 13 that Papa sent the 9's to see them and they had not been cast aside. Epsilon and the other 9's are invited by an enthusiastic Squad 13 to sit down and have some food while they explain the current situation to them.

When Ichigo voiced to Epsilon that she was afraid the 9's came to take Zero Two back, he chuckles, saying she should think of the 9's as Zero Two's former squadmates, not her babysitters.

He is present with the 9’s when Delta shows Alpha the Baby Book that Kokoro had been hiding and they later confront her. He is surprised when Ikuno slaps Alpha. They 9’s later report to Papa.

Episode 18: When the Sakura Blooms
Epsilon and he 9’s return to Mistilteinn with an APE assault team to arrest Kokoro and Mitsuru for their rebellious conduct (wanting to get married and have a child). Zero two fights them to protect her friends but they effortlessly defeat her.

Episode 20: A New World
Epsilon and the 9’s criticize Squad 13 for disobeying orders. When Squad 13 tries to rationalize the situation, Epsilon says it’s not theirs call, it’s Papa’s.

Shortly after, Epsilon and his partner Delta were killed when fighting against the klaxosaurs by VIRM.

9'δ
Delta is Epsilon‘s FRANXX partner. They work well as a pair but their true relationship is unknown. In the manga, he saves her from the Klaxosaur Princess by ejecting her from their 9 Model before he is killed by the princess. In the anime, they are both killed by VIRM soldiers.

Etymology
Similarly to Zero Two, he received the name from Papa. Epsilon is a letter in the Greek alphabet.

Trivia
9'ε 9'ε 9'ε
 * In the anime, he is killed by VIRM soldiers during the second Gran Crevasse battle. In the manga, he is killed by the Klaxosaur Princess prior to the first Gran Crevasse battle.