Miyuka Ishiwatari

Miyuka Ishiwatari (石渡 美結嘩 Ishiwatari Miyuka) is a friend of Shino Shiratsuki from Yokohama.

Introduction Arc
Miyuka first appears playing mahjong with Shino Shiratsuki and she is defeated before the bell rings. She then says it is very rare for Shino to leave early and that she'll she her tomorrow. When Shino has to move with her uncle, Shino says that she hopes they'll get to play mahjong again together.

Girls of Yumachi Arc
According to Rui Suzuki, Shino participated but just barely didn't make a qualifying spot.

2nd Children's National Tournament Arc
Shino decides to stay a couple of day with her friends in Yokohama. Rui, Miyuka, and Sanae are all present to greet her and pick her up. They decide to go to Rui's new place which is a new tower. They discuss the advantages and disadvantages to living in a high up place. Miyuka mentions that if you're coming home to pee, it's better to live on a lower floor.

Etymology

 * The name Miyuka means "beautiful" (美) (mi), "tie, bind" (結) (yu) and "noisy" (嘩) (ka).
 * Miyuka's surname Ishiwatari means "stone" (石) (ishi) and "handing over" (渡) (watari).