A Magical Girl who absolutely loves games and arcades, and belongs to Promised Blood. She came to Kamihama to investigate the automatic purification system and the Magical Girls there, but trouble often occurs because she's a sore loser and badmouthed, often causing her to pick fights with others.
The following is a summary posted on 4chan's /pmmm/ general.
Ranka infiltrated Kamihama to learn about the leaders of Magia Union so she can remove them, and if possible to dissolve the team and make it easy for Promised Blood to smash Kamihama, or at least gather intel.
She gets to meet Rena, then Momoko and Kaede by proxy, but she really hits it off with Rena, becoming friends really quick. Though there are gaps that cannot be mended, like how Ranka thinks the generosity and kindness Momoko trio displayed as they hunt witches (including giving and sharing grief seeds) is built upon her city's suffering.
Despite this, she really got close to Rena and even forget all about Promised Blood until Juri called her directly since Ranka had not made her regular report. After much struggle, Ranka decides to stay loyal to Promised Blood.
She managed to learn that Yachiyo and Iroha are part of the Union's leadership as the two are confronted by disgruntled black feathers who think they lack the spunk and will to further the system and want Touka and Nemu back as the bosses.
Ranka recklessly tried sniping Iroha and Yachiyo from afar, but the attempt failed since Momoko trio managed to warn them in time. Ranka is actually upset that Momoko trio, especially Rena is close to the leadership.
Rena's presence and Ranka slowly calming down made her decide to retreat, though after a long pause assured herself that she will not go soft next time. She looks sadly at the message Rena sent her earlier which she ignored: Rena asking her out to play as she realized the friendship is not meant to be.
Costume Stories
Ranka Chizu's Costume Stories
At the arcade, Juri is defeated once again by Ranka. After cursing out her loss, she demands a rematch, but despite winning over and over, Ranka isn’t in high spirits.
Ranka claims to have this weird fuzzy feeling, and was hoping that blowing off some steam would help, but it didn’t. Agitated by having been dragged into her plan, Juri riles her up with threats and remarks, while stating that listening to other people’s problems isn’t her strong suit, but she wants to try anyway.
Ranka says that she’s been feeling conflicted, as even though she sees all Magical Girls from Kamihama as her enemies, she can’t help but want to get along with her peers at school.
Juri tries giving her own advice, but admits that Yuna would be the better one to talk to.
Feeling defeated, Ranka leaves the arcade, but sees a crane game nearby. Since there’s a handheld game console as a prize that she wants, she decides to gamble with fate, stating that if she wins, she will try to be friendly with her fellow schoolmates.
However, it didn’t quite go as expected. Instead of winning the prize that she wanted, she dropped it, which caused a completely different one to fall down into the chute.
Disappointed, she takes out her prize, which turns out to be a baked sweet potato maker. She sighs, and wonders if fate had a different method of making friends in mind, whatever happens, happens.
