Saki Yumihara (弓原 紗季, Yumihara Saki) is Kuro Sakuragawa's former girlfriend. She works as a traffic division officer at the local police department.
Saki is a tall young woman with black hair and fair skin. In her first appearance, she has long hair and casual clothes.
After the time skip, she is slightly thinner and her hair is cut to ear length, with the exception of a long bang, swept to the right of her face. She wears both a business suit and a police uniform after getting a job as a police officer.
She is a mature young woman who likes to think things through rationally but is easily scared by yokai.
Back when she and Kuro were in high school, they started dating. The two seemed to work well together, staying together even when she headed off to college. Once Kuro joined her at college, they spent a lot of time together. She introduced him to a cafe she went to regularly and he eventually became a regular just from going with her so often. She even began to visit the hospital with him when he wanted to check in on his cousin. Some time when they're still in college together, they get engaged.
However, on a visit to a shrine, the two came across a kappa and once she learns the truth about him, she can't stand the thought of marrying him anymore, much less the thought of touching him. She dumps him and moves immediately after graduating.
She later becomes a main character alongside him and Kotoko Iwanaga in the first arc.
Hand-to-Hand Combatant: As a police officer, Saki possesses basic combat abilities. In the manga, she was shown to be able to put handcuffs on a criminal quickly.
Kuro Sakuragawa: Her high school sweetheart and former fiance. She still seems to be attached after dumping him, but after considering how much she's scared of yokai and how they might not have worked out if they didn't break up, she decides to move on. They are on good terms and can talk about whatever they need to together. However, they decide not to keep in touch after the mystery of Steel Lady Nanase.
Kotoko Iwanaga: Before even meeting properly, Kotoko has a grudge against Saki for being in a relationship with the man she wants. When they meet again a few years later, they don't seem to get along at all given the fact that Kotoko is dating Kuro now as well as being so closely involved with the very yokai that scare Saki.
When they both realize they need help with the Steel Lady Nanase case, the two put aside their differences to solve the mystery.
Rikka Sakuragawa: Saki had hard times to visit Rikka when going to the hospital with Kuro, although eventually asked him to make a visit once. During that meeting, in contrast to when she met Kotoko, Rikka was very cordial to Saki and told Kuro that she was "a good one". Upon their meeting, Saki recognizes that she slightly resembles Rikka, stating that Kuro's type "can't be more obvious" and asks if it was also the reason he wants to go out with her. Kuro later admitted his feelings for Rikka but states that he also wants her out of this world. Saki had mistaken Rikka for being dead, only for Kuro clarifies that she is not dead and never will. Realizing the elder Sakuragawa is also immortal, Saki was left fazed.