Fujiwara Michio AKA Fujiyan. He actually has two wives. Let me try to explain how it happened.
Around the time of the trip to the Labyrinth City, The conclusion of the Airship actually received help from a character that was never brought up, Christina Macallan. She is one of the daughters of the Feudal Lord of Macallan, the city where Makoto and friends live.
Nina actually hates her because Christina keeps chasing Fujiyan and she is sure that she only wants him for his money and influence because at this point Fujiyan is one huge powerful businessman already and only shows that will grow even bigger and richer.
They openly don't have a great relationship, making snarky comments occasionally, but Chris always stays close to him. Btw Chris as well went together with them on the Airship to Labirynth City.
I think it was during this trip, I don't remember exactly if it was going to the Labyrinth of coming back from it,
During the trip, Makoto approached Fujiwara, how he thought he liked Nina and noticed that Chris probably likes him.
Fujiwara says it's complicated because he knows everything because of his mind-reading power and knows they don't really like each other much so he is stuck without a good solution.
Makoto says "You are already going for the harem end huh" and Fujiwara denies it, saying this kind of situation is impossible.
As if it was happening at the same time as those conversations, when Nina was alone in the room, Christina approaches her.
Christina tells Nina to marry Fujiwara as she will as well, but she will become the first wife however both will have equal standings.
Nina gets confused, as to why a Noble would even consider being o equal standing to a beast folk since this is seen as quite disgraceful but Christina affirms that if it is not like this Fujiwara would never accept.
Nina confronts her saying she is only after his money and power, and then only now she reveals that when she meet Fujiwara, she was stuck in an arranged marriage with another noble, that only wanted ties to the Macallan Lord, and was treating her rly badly and doing a lot of shady business on her name and stuff, and was Fujiwara that managed to save her from this using his power, that's when she fell for him.
Nina was surprised, for her it was obvious to like Fujiwara because as a Beastfolk, you like beings that are powerful. Fujiwara is not much physically, but as a businessman and merchant, he is almost invincible and Nina noticed that and fell too (There is another subplot behind Nina and him but pretty sure it was not revealed in the manga yet lol).
Anyway, they came into peace and then after approached Fujiyan together and as you can imagine they became a couple.... or... husband and wife? So from this point, before the return to Macallan, he is already mostly considered married.
Back in this chapter, Lucy and Aya were discussing what to do with Makoto's situation. Actually who gives advice is Nina, because she explains how is the situation with Chris and Fujiwara and says they are pretty happy on the topic of "hierarchy" they say the three of them sleep on the same bed, and that's when come to the idea to just do all together from Aya.
That's it sorry for the big wall of text but yeah, I love this subplot that it is explored a lot in the future, but it is quite sad they will be skipping how Fujiwaara actually is quite a CHAD here boy XD