Recruitment is a little weird in Fire Emblem: Three Houses. When you select a house, you’re stuck with the characters in that house — but it is possible to recruit students from different houses, or even the teachers of the Monastery. But, to recruit students, you need to level up skills that match their particular interests. Basically, it might seem impossible to recruit characters if you haven’t leveled up particular skills.
That isn’t the case. There’s another way to recruit any character in the game, and it’s all about increasing your Support Level. Yes, you can request help temporarily from other students, give them gifts, or invite them to meals — all to increase their Support Level, even if they’re not in your party. If you manage to get a non-party student up to B-Support status, it’s completely possible to recruit them. I’ll explain more below.
This method was shared by u/runan92 on Reddit, and all credit goes to them for fully explaining this time-saving trick.
More Fire Emblem: Three Houses guides:
How To Recruit Anyone With B-Support
There’s more than one way to recruit your favorite students — and it requires a lot less grinding, too. You can recruit any student with at least B-Support status. It might take several tries, but you can save your game and try again if it fails.
To increase a student’s support status, even if they’re not on your team, there are a few things you can do. Buy them flowers on their birthday, gift them flowers cultivated from the garden, take them on battles by requesting their help, or invite them to meals.
The best (and easiest) way is to simply dump tons of flowers onto the student you want to recruit. It requires about 30 flowers to reach B-Support. It doesn’t matter how low your stats are — students with B-Support can be recruited. You can have ‘E’ level skills in everything and still get these students on your side.
When a student is at B-Support or higher, they’ll randomly ask to join you. It won’t happen every weekend, so you can simply reload your save file and retry weekends until the student actually offers to join. It’s possible to recruit multiple students per month this method — though, don’t expect to recruit more than one a week.