ara ara, you can translate as something like "Oh my"... is what is to be understood here if I'm correct😅. The other sound effects in the scene where variations of : oh 🤣. Couldn't pic up the rest because of mamoru's ara ara and: oooh OH 🤣
The dubstep in the background really intensified the conflict they were having. When I watched the first season, I was annoyed with Rin and how hung up he was about Haru. But Makoto's line to Hiyori in this season made it make sense to me. "When you swim with Haru, you'll understand."