1. Matsuri hangs out with Harumin almost every day.
2. Matsuri is Harumin's self-proclaimed girlfriend.
3. Matsuri has touched Harumin's chest at the pool. Beforehand, she also calls Yuzu using Harumin's phone.
4. Harumin play fights with Matsuri during the festival.
5. Matsuri sees Yuzu with Harumin as an "affair". (Yuzu's or Harumin's?)
6. Matsuri can talk with Mitsuko just fine (even asking if she has a driver's license).
Seeing this, makes me wishing that Harumin should get a girlfriend, Matsuri can work too.