|White Sands||Rout the enemy.|
Ryoma’s son, Shiro, can be recruited here. This paralogue can easily become a huge headache for those pushing this off because of Shiro's starting position and his AI. But no matter what level you jump into this, bring a healer capable of using a Rescue stave, and equip the Rescue. There are no ifs or buts about it, bring Rescue or you'll never be able to get Shiro into your ranks without excessive luck. This goes double for those recruiting him when they're at the point where Shiro is holding an Offspring Seal.
Shiro's AI will lead him to attack the nearest unit to him immediately. If he is sufficiently underleveled compared to his enemies, he will be one-shotted right then and there. So you have one turn to get it right. So here's what you can do. First, equip a Falcon Knight with Rescue. They are unhindered by the desert sands. Fly out as far as you can so that Shiro is within the Rescue range. Then rescue him. Pair Ryoma, his father, with another flying unit (again, don't want the desert to bother you), and then talk to Shiro, recruiting him. Then have Shiro pair up with the Falcon Knight who rescued him, so as to remove him from danger immediately. And that is the hard part of the fight and the rest is straightforward comparatively.
There are a lot of Fighters/Berserkers on this map, so make sure you keep a healer on hand. They are inaccurate foes, but they hit hard if they land the hit. No matter your level, they are known for hitting hard, but having low accuracy. And they're really good at sneaking in critical hits on top of that.
You will have access to Dragon Veins that will remove sand, thereby freeing you from your limited mobility. But this also frees up enemies too, so be careful with when you choose to do so. If you have the danger area on (the pink stuff) you will notice that when you trigger a vein, the danger area will suddenly expand. Make sure you account for that as you work your way northeast. The boss, Tarba, cannot attack from range, so I recommend you use a ranged unit to take care of him. And after all of your hard work and your expensive Rescue, Shiro will join you permanently!