5nl AK OP facing aggression

Villain here is like 14/4 over 50+ hands. Havent seen him showdown much.

PokerStars No-Limit Hold'em, $0.05 BB (4 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

saw flop

Button ($5)
Hero (SB) ($17.39)
BB ($7.19)
UTG ($5.27)

Preflop: Hero is SB with K, A
UTG calls $0.05, 1 fold, Hero bets $0.30, 1 fold, UTG calls $0.25

Flop: ($0.65) A, 4, 6 (2 players)
Hero bets $0.50, UTG raises to $1.65, Hero calls $1.15

Turn: ($3.95) 3 (2 players)
Hero checks, UTG bets $3.32 (All-In), Hero???

I know turn raises usually mean a monster, but why limp UTG and raise the flop? Something about his line bugs me, so I'd probably be calling here and hope he hasn't got 33.

Who limps UTG with Axs? A9s+?

Your def beat on the turn imo.. As far as how to proceed on the flop.. I'm unsure.. But will post back later maybe.

He obviously has 25o and has hit his guthshot straight draw.

All jokes aside however, I would usually say he's hit his set. He was trying to limp into the pot with 44 or 66 and you raised him. He saw that you had a nice juicy stack to double up on if he hit his set (and also realized you are raising with goodness, yes goodness) and chose to call (though a questionable call). Flop comes...BOOM, SET! Get outta there! I had a hand similar to this yesterday (posted on my OP).

Hero can still get away from his hand. He's getting just over 2-1 with top pair top kicker on a co-ordinated board.

Why do you think we're committed sportsmen?

Is it possible he had nut flush draw on turn plus the paired ace?
Maybe its just me.....I always assume opp's have flushes...
perhaps he did limp with ATs or something similar and then call your raise.

meh. He's got you here and you can easily get away from this with minimal damage done. There isn't enough for you to win here if you make this call imo. Fold and move on.