Yul reveals he met Naksu as a child
Yul tells the Songrim leader of a girl hiding in Danhyanggok whose father wrote down the stars, and learns of a recorder killed by the four families.

Every Alchemy of Souls moment featuring Seo Yul, in story order. Played by Minhyun.
134 moments · 5h 00m · by Favseen
Moments 31–60 of 134
Yul tells the Songrim leader of a girl hiding in Danhyanggok whose father wrote down the stars, and learns of a recorder killed by the four families.
Ju-wol admits Mu-deok tried to sell Uk's Spirit Plaque; Mu-deok tells Yul she wanted money and fun, and the plaque is then tied to Naksu.
The Crown Prince is told the maid broke the yin-and-yang jade meant for the wedding rings and fled, then Yul turns up looking for her too.
An apparition of Mu-deok tells Yul he kept the whistle and never stopped longing for the girl from Danhyanggok, then dares him to banish her.
Warned the vault's relics can trap anyone forever, Yul and the Crown Prince insist on going in with Uk, and are given one hour.
The Crown Prince teases Uk about inheriting Jinyowon's treasures, a noise startles them, and calm Yul marches off the wrong way.
Comparing notes on the illusion, the Crown Prince learns the sachet he gave Mu-deok has been put to use keeping flies off the outhouse.
As the door is about to be sealed, Yul is sent to drag Uk out while Uk tells the mirror his plan to keep her by his side, and that he misses her.
Uk ties a cloth over Mu-deok's dazzled eyes, then Dang-gu, Yul and the Crown Prince each arrive offering to take her for treatment.
Piecing together the illusion's words and memories of Danhyanggok, Yul concludes the shifted soul in Mu-deok is Naksu and that she is alive.
Following Gwigu to the site of the soul shift, the mages find traces of the Soul Ejector and Uk's binding bracelet, and fear the worst.
Yul hands back the bracelet and reveals he wounded then saved Mu-deok; she invents a story that Uk abandoned her, and he plays along.
After telling Uk to lie low until the duel, Yul coldly notes she was at Uk's side again, and Mu-deok bites back.
Asked whether the maid saw the spell, Yul says she is an ordinary maid who would not understand it, and hides a hand hurt by the Soul Ejector.
The Crown Prince learns Mu-deok sold his gift, claims sole rights to her nickname, and sees the capital wearing Naksu's blue cloth.
Lost and a little drunk, Yul confesses he has gone astray, lets Mu-deok lead him, then asks about the illusion that said she loved him.
Master Heo signs Uk up as a marriage candidate, then learns he wanted Naksu as a master and would use sorcery to save a life; he demands his energy back.
As drunk Uk is carried in, the gate guard rules a maid cannot enter and a trainee cannot leave; Mu-deok begs to be taken along.
Uk drunkenly calls for her inside; outside, Mu-deok swears she will kill him if he abandons her, and Yul carries her vow to get into Songrim.
Uk starts basic training under the regulations; Maid Kim beams with pride, then lists everything Mu-deok did for him and says she is better off without him.
Uk finds the new book empty; the others explain it only reveals itself to focused energy and mock him until Yul cuts them off.
Yul visits Mu-deok to reclaim his lost umbrella, talks about his old leg wound and a friend from Danhyanggok, then makes her pay up.
Go Won and Yul get the test papers and solve them, working out a tricky seating puzzle and how to wash ink from clothes.
Dang-gu finds the whistle Yul left at Danhyanggok in Mu-deok's bag; Yul lets her keep it and dares her to make him believe her love.
Yul says real love is hard to say even once, and reveals the whistle belonged to a friend he failed to confess to.
At the cremation Park Jin has Yul pour energy into the body; it turns out to be a soul shifter, and Songrim claims the case.
Park Jin confronts Jin Mu over the cover-up, then the rampaging soul shifter fights until Cheonbugwan strikes it down.
Yul tells Uk he slashed a soul shifter and that mages must protect the world from monsters; Uk offers a gentler view.
Songrim's crew keeps redoing the basin repairs to stay inside, and Jin Mu probes Seo Yul about mastering Chisu.
Told Seo Yul is out of her league, the vagabond So-i muses that as Jin Bu-yeon she might have a chance with him.