By 
Ninae will not join your party in Fire Emblem: Fortune’s Weave unless you are willing to get a Paradise Fish for her. Given the size of the game and nature of gathering points, it’s entirely possible you won’t even have seen one by the time you get the Support and Renown levels high enough to recruit her. Here’s where you can pick one up.
Where can I find a Paradise Fish in Fire Emblem: Fortune’s Weave?
In order to get this specific fish, you need to head to the southern points of the map. The Paradise Fish is the rarest catch if you search in Lake Brontes in Fire Emblem: Fortune’s Weave. That’s just east of the city of Alecto and in an area where there tend to be enemies that are around level 25-30. If you’ve already unlocked it, the easiest way to get there is to take the carriage to the Salacia Posthouse, which is right around the corner from Alecto, then walk over. It should only take about three or four turns to walk from there.
Here’s where you’ll find that lake on the map. It took me three tries searching to get one. Fortunately, you only need to catch one to recruit her.
Ninae is a rather useful unit in Fire Emblem: Fortune’s Weave, so she’s worth the trouble. She has the unique Personal Ability called Spirits’ Voices, which grants her +10 Avo and +10 Hit if she’s facing a foe who uses Attack Magic in the fight. She also has a Spirit’s Guidance skill that will give adjacent allies that same perk. She’ll arrive as a cavalry unit, and I found she’s incredibly useful if you shift her over to a flying mount when you change her class after she levels up.
Fire Emblem: Fortune’s Weave is available on the Switch 2.
