Tire Problem

Yup, replace and don't worry about it. That tire is ROACHED. Shinko won't care -- they'll tell you, correctly, that it's worn out and not their problem.

As a reasonably educated guess, I'd say the PO rode around with badly underinflated tires.

I once changed tires on a Wee with 705s. The bike arrived (after a 45 minute highway trip to my house) with 17psi in the front and 19psi in the rear. The front had a very, very weird wear pattern a lot like yours. And yes, the tires were very warm... made them super-easy to remove, anyway. The owner had somehow never, not once, thought to check tire pressure.

The other thing to bear in mind is that strange front tire wear patterns are very, very normal for knobby and blocky tires that see significant pavement use. If riders don't have experience with this, it's unsettling. Over on ADVrider.com panic and anger over perfectly normal funky front tire wear is a super-common topic.

The physics of front tire wear on motorcycles is very strange, counter-intuitive, and poorly understood, with tons of absolutely brainless Crusty Olde Byker Legends passed off as fact. I won't get too far into the topic here, but all you need to know is that all front tires wear out in very different ways than rear tires, there's always some sort of regular-ish scalloped pattern to it, more wear on one side is perfectly normal, and that tread design and depth make a lot of difference in what you see.

When you start to see and feel front tire wear, whatever the amusing wear pattern is, it's time to replace. And the corollary is that it's rarely worth trying to use up two rear tires for every front; I've pretty much given up on that and always replace motorcycle tires in sets.