Information about leveling and units. May contain some slight spoilers.
Do NOT use bonus XP to level up a character directly!!
Much as in Falnarion Tactics II, actually gaining a level from bonus experience will ignore their growths and cause them to only gain three points in more or less random stats, while almost all characters in Tales of Beasteria have much better growths, often gaining in almost every stat and/or multiple points in a stat. Only raise characters up to 95 or so XP, so their next attack in a combat will cause them to gain a level. (96 at level 9)
However, there is another trick you can use here, which also works in Falnarion Tactics II – Utility Hammers can be used in the base menu, and cause you to gain 5 XP, and count as “real” levelling, not bonus XP levelling. So, if you have items left to repair, you should give the item to someone who you want to level up, set their XP to 95 or higher with bonus XP, and then have them use a Utility Hammer.
Usagi’s promotion is quite dubious, but going from a mediocre beast weapon user to a bad mage with big Skill/Speed stats and movement is… not awful?