[Chekov and Ianto know each other, of course. Even if the dome wasn't as small as it is, they both spend enough time in the library and with Kitty that they inevitably cross paths with some frequency.
Chekov approaches him at the coffee shop, smiling uncertainly. He knows that he hasn't been the most cheerful company lately; sometimes he's hesitant to inflict himself on people who aren't close friends.] Ianto, hello.