I am very interested what is the name of the song played, when Fubuki and Mutsuki decided to talk to each other during a night walk. Yuudachi with Sendai sisters join them later and all of them make 'Torpedo Soul' pledge. It was just before all of them are going to be reassigned to new fleets.
It was in episode 5. Starts at about 3:20 and ends at 5:11.
I already figured out that composer is most likely to be Natsumi Kameoka (亀岡夏海).