Lachinn

Lachinn is the het ship between Finn and Lachesis from the Fire Emblem fandom.

Fire Emblem: Genealogy of the Holy War
Finn is a knight of Leonster who is loyal to Leonster's Prince and Heir Quan, and later followed Quan to join with main protagonist Sigurd. Lachesis, meanwhile, is a noblewoman from Augustria's House Nordion and the half-sister of Eldigan, whom she has romantic feelings for. In-game, she is able to marry Finn if they reach enough "love points," a mechanic in Genealogy that works similar to supports. At one point, Sigurd is accused of being a traitor of the crown of Grannvale and is forced to flee to Silesse with his allies, including Finn and Lachesis. After hiding in Silesse for one year, Finn leaves Lachesis to return to Leonster along with Quan and Ethlyn, who decide to bring reinforcements back to Sigurd. Leonster, however, falls to Thracia, prompting Finn to flee with Leif (Quan and Ethlyn's infant son). Meanwhile, Lachesis decides to send her son Diarmuid (that she had with Finn if they were paired) to safety in Isaach. She is one of the few survivors of the Battle of Belhalla, and fled to Leonster after the battle's end. Here, she has her second child, Nanna, and raises her with Finn, alongside Leif. Lachesis eventually decides to cross the desert alone to reunite with Diarmuid, but disappears en-route, with her ultimate fate unknown.

Finn eventually supports Leif in his battle against the Granvalle Empire as his retainer and guardian. At one point, Finn also has a conversation with Nanna if she is his daughter: Finn remarks that Nanna's strong determination reminds him of her mother. Nanna then asks Finn why he allowed Lachesis to try to cross the desert alone, to which Finn answers by replying that it's only between him and Lachesis, and that Nanna will understand when she is older. After the war, Finn returns to Leonster, and after Leif had become king of the unified Thracia, he spends three years in the Aed Desert, possibly searching for Lachesis.

Mitsuki Oosawa manga
While Finn and Lachesis have no special interactions in-game, the Mitsuki Oosawa manga adaption gives them a romantic relationship.

Finn is originally introduced to Lachesis as her personal bodyguard, assigned to her by his master Quan, and immediately develops strong feelings for her. While attempting to set up a tent and failing, Lachesis is helped by Finn, who teaches her how to set up a tent properly. Later he also figures out about Lachesis' feelings for Eldigan, and admits to being jealous of those feelings.

After Eldigan's death, Finn finds Lachesis next to the coffin containing Eldigan's body just before it is to be buried. Finn tells Lachesis to take better care of herself, which Lachesis shrugs off and almost immediately asks Finn to kill her as well. An appalled Finn immediately slaps her and leaves the room, upset that she would even suggest that of him. Lachesis continues to sink into despair and begins to isolate herself, while Finn, desperate to bring Lachesis out of despair, tries to get Lachesis to eat and tells her how worried everyone is for her, himself included. Finn is later teased about his apparent feelings for Lachesis by Ethlyn.

When Lachesis wishes for a white rose, Finn draws one on a paper, as white roses in the current season would be unable to grow. He later takes drastic measures to snap Lachesis out of depression, first by trying to force Lachesis to eat, then by stabbing himself with the Lands Sword while Lachesis was holding it, trying to illustrate that the reason Eldigan gave it to her was because he wanted her to live. The latter action mortifies Lachesis and causes her to heal Finn, alongside allowing herself to finally accept and move on from Eldigan's death.

Later, Lachesis decides to train to become a Master Knight, her promoted class in Genealogy, and trains with Finn in lances, growing even closer to him in the process. When she finds out that Finn will be returning to Leonster with Quan and Ethlyn, Lachesis becomes upset over losing one of her closest allies, although she does not fully realize it and silently questions why she is suddenly so distraught. Finn later meets with Lachesis one final time while she is training, and one of the training sticks she is cutting flies off and hits Finn's hand, prompting her to wrap the wound in gauze. She also takes the opportunity to admit how hard it is to imagine that she might never see Finn again, as he was her closest confidante who "brought the color back to her world" and that she took Finn for granted.

She then asks Finn to at the very least not forget about her in Leonster, to which Finn responds by confessing his feelings for her, saying that he can no longer lie to himself about them. The two of them then share a night of passion as Lachesis asks Finn what Leonster is like, as Finn describes Leonster and his wishes to take her with him, though he cannot due to his commoner status. As such, Finn promises to return for Lachesis once his status has improved, which Lachesis responds by saying she will wait for him. Lachesis later finds out that Finn left Lachesis with her first child, Diarmuid.

Oosawa Manga

 * Upon learning of Lachesis’ feelings for Eldigan, Finn admits to himself that he envies those feelings.
 * After Eldigan’s death, Finn expresses concern for Lachesis’ well-being after she stops eating from depression. Ethlyn finds out about this and teases Finn about it.
 * After trying, and failing, to force Lachesis to eat, Finn stabs himself with the Lands Sword while Lachesis was still holding it as a last resort to heal her, as anyone stabbed by the sword has their life essence transferred to the holder. Lachesis is mortified by this and heals him, while finally letting go from Eldigan’s death.
 * While training, Lachesis accidentally wounds Finn and treats his wound, taking the opportunity to tell him that he was the one person that “restored the color” in her world. Finn also takes the opportunity to confess his feelings for Lachesis, which she reciprocates.
 * After Finn’s confession, the two of them have sex (resulting in Diarmuid’s eventual conception) just before Finn leaves to return to Leonster, promising Lachesis that he will come back for her once his social status improves.
 * As Finn prepares to leave with Quan and Ethlyn, he and Lachesis exchange one last smile before parting. Ethlyn notices this and teases him again, flustering Finn.

Fanon
Lachinn is a very popular ship within the Genealogy fandom, partially owing to the fact that, in Thracia 776, Lachesis' daughter Nanna refers to Finn as "father", strongly implying that Finn and Lachesis were romantically interested in one another. While this has been debunked as Nanna is moreso Finn's adoptive daughter, Lachinn remains a popular pairing in the Fire Emblem fandom; It is the most popular pairing for both Finn and Lachesis, with its only rival being Lachewolf (Beowolf x Lachesis) on Lachesis' end.

In Japan, the ship is among the most popular Fire Emblem ships overall, and was consistently talked about in early online chat rooms, although shipping wars between it and Beowolf x Lachesis were common. Finn and Lachesis themselves are also among the most popular Genealogy characters.

There are theories that Nanna is Finn's daughter, while Diarmuid, Nanna's brother, is Beowolf's son. This is due to the fact that in Thracia 776, Diarmuid starts out with the "Beo Sword," a sword strongly implied to be connected to Beowolf, as the only other person capable of equipping it is Fergus, who is rumored to be Beowolf's illegitimate child. This theory is further supported by the fact Nanna can't equip the Beo Sword, likely meaning Beowolf isn't her father.

Fandom
FAN FICTION

FAN ART

Other
 * Makkou Exploration, a (now-defunct) Japanese fan-site dedicated to the ship, created by the artist Okumi.
 * The Second Son Committee, a Japanese fansite for the ship dedicated to Valand (ヴェールンド), a child OC.