Seol took full advantage when Derek McInnes lost possesion with a poor back pass and the South Korean was able to round Lenny Pidgeley to score.
Millwall: Pidgeley, Phillips, Craig (Ross 46), Elliott, Robinson, Whitbread (Lawrence 83), Dunne, McInnes (Cogan 46), Brighton (Hackett 46), Byfield (Williams 67), Hubertz (Braniff 76)
Subs: Day, Shaw
Reading: Federici, Murty, Makin, Ingimarsson (Ujah 88), Gunnarsson (Pearce 71), Halls (Cox 60), Sidwell (Osano 55), Little (Davies 76), Oster (Shorey 55), Seol (Long 46), Lita (Golbourne 65)
Sub: Stack