I can understand Aqua's behavior quite well, based on the first ep. Even if he doesn't know Ruby is the kid he once lost as a doctor, he still knows he doesn't want to lose another important person. He's also pretty disillusioned because he was already old enough in his previous life, so he was never going to live the dream-filled teenage years for a second time. Especially after he watched Ai getting murdered. Ruby, or rather Sarina, died quite young, so she's now living her teenage years for the first time, so obviously she's going to have her head in the clouds. That's a truly fundamental difference between the two.
Nevertheless, I feel like the director was saying something important to Aqua, so it's a crying shame the I-don't-care mother interrupted them time after time. I don't understand how the director can keep living in the same house with her. There are lots of abandoned houses/apartments all over Japan, including Tokyo, due to the shrinking population, so he should get a place of his own. It's not like a director needs to live in the middle of Tokyo anyway. He's not going to direct movies in his own house, and where he edits them afterwards doesn't matter one bit.
It's difficult to expect overly exciting school time from Aqua, though. Having been a physician in his past life, he must have cleared everything, including university, decently enough, so it must be annoying for him to go through it again. I doubt he finds the other students that interesting either, having an adult's mind himself.