User blog comment:KodachiZero/Chain Chronicle V3 on the Wiki + Q&A/@comment-201.186.98.228-20161211012539/@comment-26432452-20161211042220

It's all random chance but make sure you have all the req.

- receiving arcana must be from book 3 and have 10 or more affection point.

- teaching arcana must have denju tab on info and at least lv 40 or above.

- both teaching and receiving arcana must be on the same class.

After that just put them on the same party, position doesn't matter so you can even put the teaching arcana on the sub and pray to RNG every time you finished a battle Lol.

Also, make sure there is only 1 pair of eligible teaching-receiving arcana on your party. Since it is random, your receiving arcana could learn from any eligible members on your party if you put more than 1.