At the risk of starting a riot . . . the two boys Lanyon is walking with are Enfield (stage right) and Utterson (stage left). For fear of Utterson-baiting, I am obligated to inform you that this is the only time in this chapter that Utterson will be appearing—he is a glorified incidental, nothing more. Sorry!
It’s funny to imagine Utterson as a member of Lanyon’s rowdy schoolboy crew, as Utterson is canonically not into anything that could conceivably be labeled rowdy. I imagine him as the One Reliable Friend who nonjudgmentally accompanies Lanyon and Co. out, orders nonalcoholic beer, and spends the next day tracking everyone down to pay their share of the tab that he definitely picked up.