They hit you over the head with it and the extras at the end outright said it when it showed Irene. I wonder if Bob died or something since Nancy has his last name still but she said that Irene raised her alone. He didn't come off as the kind of guy who'd abandon his kid. Still, definitely a crazy plot to bring back considering how long ago it was.
Also damn, Nami's a professional young woman now. We've seen her grow up through all these volumes. And it's nice to see her proactively involved in a major way in a story arc.
Technically not his kid, so maybe he just drifted apart from Irene for other reasons? We'll find out soon enough. Well, not that soon enough because damn what a cliffhanger for the volume, I almost want the scans team to switch to chapter releases... (kidding, but usually Shima story arcs have matched up pretty closely to volume releases).
And yeah she's got her dad's tough nature, but thankfully not his manwhoring ways.
Curious who she slaps first, her dad or Irene.
Honestly I've been looking forward to seeing Irene and what happened with her kid again for some time, though not as long as original readers had to wait at least.