The Resolve (Turn) of the Younger Sisters (妹たちの決意（ターン）, Imōto Tachi no Ketsui (Tān)) is the fourth episode of Hyperdimension Neptunia: The Animation. It was first aired in Japan on August 2, 2013.
In the waste disposal plant, Arfoire and Warechu reveals themselves to the entrapped CPUs. After hearing that one of the Anti-Crystals was taken from Lowee's Basilicom, Blanc reveals that she knows about the crystal but doesn't know that there's more than one. The Anti-Crystals are draining the Hearts' powers, eventually reverting them back to their human forms. Nearby, Nepgear and IF retreats due to the overwhelming amount of monsters.
Nepgear and IF manages to return to Leanbox. IF contacts Histoire and asks her to do some research about the Anti-Crystal. The CPU Candidates worry about their sisters. Feeling as if it's her fault, Nepgear tells the group how she thought that the dizziness she had before was due to the Anti-Crystal she picked up. Uni also puts her at fault and leaves the room.
Back in the waste disposal plant, Neptune becomes bored and gets Arfoire's attention. Then Arfoire show the CPUs how they're slowly losing their powers. Black liquid is shown to be dripping out of their bodies, making the pool of black liquid below them.
Nepgear is shown outside a balcony. Uni comes back and apologizes to Nepgear. Nepgear, Uni, Rom, and Ram unite and plan to free the CPUs. Using Vert's game system, the younger sisters, with Compa and eventually IF, train in combat and attain the ability to transform. Abnes later interrupts and plans to let Rom and Ram go back to being "normal little girls." She is immediately involved in the girls' training after Rom and Ram insists her to "play with them," posing her as a monster in the game. They later train using the game's AI system, defeating monsters like an Ancient Dragon. The CPU Candidates plan to train some more, but IF stops and shows them the pictures of the confined CPUs, which they assume might cause a crash in shares. They plan to liberate the CPUs right away.
The CPU Candidates, IF, and Compa arrive in the waste disposal plant. Fighting their way to the Hearts, the group tries to overcome an overwhelming amount of monsters. Feeling inundated by the monsters, Nepgear feels at fault and leans on her sister to help her. Momentarily, she concludes that she relies on her sister too much and is afraid to become stronger than her. She gains her resolve to her feeling, enabling her to transform into HDD form.
- The CPU Candidates unite to prepare and rescue the Hearts by training together.
- Nepgear transforms to HDD form.
Rather than revealing a tied-up Neptune, IF accidentally reveals the CPU Candidates a picture of Compa in a nightgown, who's sleeping in a bed. Nepgear blushes, and Uni is surprised. Rom and Ram tries to see what the picture is. Then IF realizes her mistake in the picture and reacts in embarrassment. She tells them to forget what they saw and tries to clarify with haste about why she took the picture, stating that she only happen to take a picture of Compa when they had a sleepover.
The CPUs are confined in the waste disposal plant in Zune District. In Vert's residence, Nepgear, Uni, Rom, Ram train with IF, Compa, and Abnes using Vert's game system. The group travels to the waste disposal plant and try to liberate the CPUs.
Characters are shown in order of appearance.
- While Neptune also tries to recall Arfoire's name, she calls her "CFW Magic" when she tries to get Arfoire's attention.
- This is the last episode to feature "Go Love & Peace" as the ending song.