^ I am only hard on Taichi in this case because his confusion may hurt somebody. But who knows how they'll handle it? Maybe he finally realizes his feelings for Chihaya and breaks it off. The girl gets hurt, but it's the best thing for everyone. Or maybe he find outs out while he does care for Chihaya he has moved beyond being in love with her and decides to stay with his gf (I doubt it). The worst is for him to stay with his gf while his feelings for Chihaya grow as they spend more time in the kurata club (it's almost guaranteed that they will make one now). That's really dangerous...
It doesn't help that while the gf seems nice, she absolutely paled in comparison to Chihaya in terms of looks and personality. It made sense why she was so semi-jealous: "Hey, who is she???"
On another note, I thought it was interesting how Chihaya had Arata's phone number but never bothered to call until now. It implies that they all had each other's contact info. but didn't talk since they were kids. That really is like real life, isn't it? I've had super close friends who I've parted ways with, and while it was totally possible for me to contact them (and vice versa), we never bothered. Then after years and years you think of calling them and think, "Wait. This would be really awkward. What would we talk about!?"
Then you decide to pass on it.
It's not that you no longer like the person, but your life has changed and you have moved on. This probably isn't the case for Chihaya and Arata though. Chihaya really believed in being reunited with them and thus continued to play so that she would be good enough to compete with them. And Arata probably just wanted to keep his good childhood memories locked up because it's a painful reminder of how bad he has it now.
Another note: I love the VA for Arata's mom. I wish she was featured in more anime nowadays.