Villain is unknown but after just 12 hands he's 50% vpip

River line?

PokerStars No-Limit Hold'em, $1.00 BB (5 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

Button ($71.75)
SB ($63.60)
Hero (BB) ($152.35)
UTG ($103.45)
MP ($96)

Preflop: Hero is BB with 7, Q
1 fold, MP calls $1, Button calls $1, SB calls $0.50, Hero checks

Flop: ($4) 3, 6, 7 (4 players)
SB checks, Hero bets $3, 1 fold, Button calls $3, 1 fold

Turn: ($10) 7 (2 players)
Hero bets $6.75, Button calls $6.75

River: ($23.50) J (2 players)
Hero ?