KK fold on unders

[arkady]

SB here is passive, he shows aggression pre flop but then shuts down if misses post.

Party Poker 10/20 Hold'em (6 max, 5 handed) converter

Preflop: Hero is Button with K[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img].
UTG calls, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises</font>, SB calls, <font color="#666666">1 fold</font>, UTG calls.

Flop: (7 SB) T[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, UTG checks, <font color="#CC3333">Hero bets</font>, SB calls, UTG calls.

Turn: (5 BB) 8[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets</font>, <font color="#CC3333">UTG raises</font>, Hero folds, <font color="#CC3333">SB 3-bets</font>, UTG calls.

River: (11 BB) 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">UTG bets</font>, SB folds.

Final Pot: 12 BB

Either the SB is really good or really bad. I am clueless here.