Absolute/UB Cereus No-Limit Hold'em, $0.10 BB (6 handed) - Absolute/UB Cereus Converter Tool from FlopTurnRiver.com

Hero (Button) ($22.18)
SB ($29.45)
BB ($20)
UTG ($7.66)
MP ($7.52)
CO ($11.81)

Preflop: Hero is Button with K, K
UTG calls $0.10, 2 folds, Hero bets $0.50, 1 fold, BB calls $0.40, 1 fold

Flop: ($1.15) 4, 7, 2 (2 players)
BB checks, Hero bets $0.70, BB calls $0.70

Turn: ($2.55) J (2 players)
BB checks, Hero bets $2.10, BB raises to $6, Hero ????

Right, Villain here is 28/6/0.3 through 50 hands or so. When he reraised, considering he was normally so passive and the flat call on the flop, the turn I knew my kings could be dead to a set or two pair. Call and c/c river? c/f river? After all he could have floated AJ, KJ, QJ due to the low flop, thinking I may have missed too - he could even be betting a flush draw? I'm a bit lost (obviously).