"Amazing!" Tintin says in quite accented English. He switches back to Mandarin. "Then perhaps we can arrange to help each other more formally! It would be nice to have such an arrangement so early."

"Oh, yes, it would be lovely to have an arrangement!"

Does this kid want English tutoring. Nie Huaisang guesses that's one of his limited skills.

This kid absolutely wants English tutoring. He wants English tutoring badly enough that he is willing to take on a dangerously open-ended deal with an obvious flake who at least speaks the damn language.

"I will assist you with the parts of alchemy assignments that you are having trouble with if you will agree to spend at least an equal amount of time helping me learn English to a satisfactory level, subject to renegotiation once my level of English fluency is mutually agreed to be satisfactory, if we have three or more lab accidents which could cause serious bodily injury, or by Christmas."

"We have ourselves a deal."

Kid does not take pity on useless people. Dammit.

(That was a substantial amount of pity, actually. If pity were not involved Tintin would not be making this deal at all.)

Tintin smiles. "I look forward to a mutually beneficial arrangement." Then he bows and - consciously does not scamper off, because that would still be rude. He walks away. At a reasonable pace.