No reads on villain, I hadn't been playing with villain much before hand.

Party Poker No-Limit Hold'em, $ BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Hero ($23.05)
Button ($3.10)
SB ($26.88)
BB ($33.95)
UTG ($21.45)

Preflop: Hero is MP with K, K. SB posts a blind of $0.10.
1 fold, Hero raises to $1, 1 fold, SB (poster) calls $0.90, 1 fold.

Flop: ($2.25) 7, T, 6 (2 players)
SB checks, Hero bets $1.75, SB calls $1.75.

Turn: ($5.75) 5 (2 players)
SB checks, Hero bets $3, SB calls $3.

River: ($11.75) 5 (2 players)
SB bets $21.37 (All-in)
Hero ???

Did villain catch his flush or was he slow-playing a set???
Suggestions?