You run into Hiro at least once in Eiyuden Chronicle: Hundred Heroes before you can recruit him in the Abandoned Mines. He will bring a very important asset to your HQ as you go about your quest.
Hiro is in the Abandoned Mines Mid-Point on the east side when you get teleported in.
When you enter the mid-point you'll see three circles in the bottom southeast corner of the map. To get to Hiro, you'll need to go up to the second floor from the middle tower, and back to the left tower to get to the third floor via the west opening. Using the northern path that connects all three towers, go to the right tower and use the opening on the east side to go back down to the second floor and work your way around the back to talk to Hiro. From here he will join the Alliance.
Hiro runs the tool shop once you build the blueprint. He will have many of the items you'll need to heal and restore as you fight enemies across the lands.