big pot versus super lag live

[LAgambol]

10/20 NL
Hero has 5K, villain covers

villain is big korean gambler, he plays nuts and air the same. hero has been playing semi LAG, but we have big pot history.

Hero has AdKd
1 limper, hero in MP makes it 100, CO calls, button calls, villain in BB makes it 400, EP limper folds, Hero calls, others fold

Flop:
6d 3d 6s
Villain bets 500, Hero makes it 1900, at this point villain kind of stares at me, mumbles something, counts his 100 dollar bills and then calls. doesn't necessarily seem like a slow roll.

Turn: Kc
villain checks, Hero checks

River: 8 c
villain looks at board, then me and quickly goes all in, hero calls