Quote Originally Posted by Kraco
I feel sorry for Arata; he still considers Taichi one of his good friends, just like Chihaya, and doesn't have any idea Taichi probably hates him already at some level. They don't interact, let alone meet, so much anymore that it would have any immediate consequences, but it's still a pitiful situation, and I hope Arata won't need to learn the truth the hard way or during any critical moment
It goes both ways. Arata thinks of Taichi as a friend (I wouldn't say Taichi doesn't consider Arata his friend, but he considers him "dangerous" more than anything else), but Taichi has a friend who he can't accept 100%. Taichi is popular, but he doesn't actually have many real friends. The original trio are the closest, but Chihaya is oblivious to his feelings and Arata (unknowingly) threatens them. Taichi is the most observant and sees the entire picture, but is feels powerless about being able to clean up this mess.

I don't think Taichi "hates" Arata, but he feels extremely insecure and (thinks he) knows that if Chihaya had to make s choice out of the two, he's out. Despite having everything from good grades to money and looks, Arata stands as a constant reminder of what Taichi really wants*, but could never get:

1) Chihaya's attention.
2) Excellent karuta performance.

(* mostly #1)

We can take Taichi's comment two different ways:

"What am I doing here?"

-What am I doing playing Karuta (when I'll never be as good as Arata or Chihaya) anyway?
-What am I doing in B-class, when all my real targets are in A-class?

The second situation would be funnier, if the two meet at the finals and Retro gets owned because he interpreted Taichi's sigh wrongly.