Inu calmly slotted the point from about 30 metres out as the Bulldogs tightened their grip on the NRL minor premiership with their 12th consecutive win.
But the game, played in front of 29,194 fans, was marred by a video refereeing decision by Sean Hampstead, who awarded a 74th minute try to Bulldogs winger Jonathan Wright.
The lanky flyer dived over in the left corner after Frank Pritchard ran behind Josh Morris who appeared to have impeded Tigers centre Blake Ayshford.
Tigers captain Robbie Farah exploded after the decision was made.
"Since the day rugby league was created you cannot run behind a player ... it's a shepherd," Farah told the referees.
The Tigers did a great job to stay in the contest with prop Aaron Woods' converted try in the 78th minute locking the scores at 22-22.
Canterbury went into the halftime break with a 12-6 lead after two brilliant long-range tries to Aiden Tolman and Josh Reynolds.
The joint venture pegged a try back just before the break, to winger Marika Koroibete, before a sensational opening to the second half resulted in the Fijian flyer scoring his second try on 45 minutes.
Soon after, Reynolds put Inu through a hole down the right edge before the centre linked with Ben Barba who scored on 55 minutes with Inu converting to make it 18-10.
The Tigers had raid after raid repelled by the Bulldogs before Blake Ayshford produced a nice inside ball to send Marshall over for a converted try to make it 18-16 but they lost momentum when Tim Moltzen dropped the re-start.