The visitors took an early lead through James Harrison but Hiwula equalised before the break.
City’s in-form talisman then went onto score again, before Adam Drury made it three and Hiwula sealed his hat-trick to send the Blues through to the fourth round of the competition.
Corby started brightly, with Harrison producing a looping header that almost beat City goalkeeper Angus Gunn after just three minutes.
The Steelboys, encouraged by a vocal travelling support, dominated the opening 20 minutes and their efforts were rewarded when Harrison lifted the ball over Gunn.
The lead was deserved as City struggled to impose themselves against the tenacious visitors. Despite that, Adam Sadler’s Blues remained focused and equalised through the Under 18’s top scorer Hiwula 10 minutes later.
Although Corby kept their heads up and displayed dogged determination, the combined creativity of City’s Alex Henshall, Denis Suarez and Albert Rusnak was always going to threaten and proved the key to the Blues’ victory.
After the break the home side found momentum and took the lead when Hiwula slotted home after Suarez’s effort was saved but not cleared by Corby’s goalkeeper Danny Wallace.
City maintained possession well and soon it was three when midfielder Drury slotted in Rusnak’s cross from close range.
Corby began to tire in the latter stages and the Blues youngsters pressed on, with Hiwula grabbing his hat-trick with eight minutes to go.It was a valiant effort from the visitors but Sadler’s team deservedly goes into the hat for the next round.
