[That makes him giggle a little] Practical has nothing to do with it, that's why. [He smiles, understanding that]
Take my brother for example. [He looks up at Agito] My father taught me everything I know, and thus everything Agito knows. So logically, Kaito is useful and could be again. However Agito hates him. So even if he can be useful, if given the chance, Agito would kill him. [Akito's very calm about this. He accepts what his other is, even if he disagrees]
The only reason he hasn't is because he cares for me, and he knows it would upset me if he did. So his emotions rule what he does in relation to Kaito, rather than would be sensible. [He looks at Tieria again] So sometimes you have to factor in emotional response, as well as logical.