Arthur's marriage event shows up randomly after completing all of the Dating and Marriage Requirements. It is called "Transient Vision".
The event begins by walking into Arthur's office, where Frey will find Vishnal waiting to deliver a message. As Arthur is not in at the moment, however, Vishnal asks if Frey could deliver the message, instead. It concerns some troubling rumors going around that the king has heard of the "prince-swap" at the beginning of the game and has sent an official investigator to confirm them. Vishnal also brings to light a rumor about Arthur not being a legitimate prince, but rather born to a mistress. After relaying the message, Vishnal leaves Frey in the office.
After Frey leaves the office, Arthur will return to it. Entering the office again and talking to Arthur will trigger the next part of the event, where he assures Frey that there's nothing to worry about and invites her on a date set for tomorrow, whenever it suits her, ending what the player can advance for the day.
The next day, (assuming the player doesn't forget) talking to Arthur at any time will continue the event. He'll have Frey try a new tea he is planning on selling, and she can either say that "It smells nice!" or "It has a unique taste!". Afterwards, Arthur goes on to explain his job the way he sees it. After finishing his explanation with a quote somewhere along the lines of, "This tea, for example was meant to be shared with loved ones, and you're the first person I thought about," he then asks about Frey before offering to answer questions about himself, which presents the following options:
- "What's does it feel like to be a prince?"
- For this one, Arthur will admit that he never truly felt like a prince, and that his brothers were quick to point it out. At Frey's next question about Arthur having siblings, he answers that he does, and that they are all good people.
- "Let's talk about glasses."
- After clarifying that Frey was curious as to why Arthur was so fond of glasses, he deflects the question by saying that he would be positively embarrassed if he said it out loud, and politely refuses to comment, despite her insistence. After asking this question and the former, it will unlock the final question.
- "Tell me about your family." (must ask the other two questions, first)
- Arthur will point out the by now well-known fact that he is a prince, before making a joke about not having a mother. He does not go in-depth on this question, and soon ends the date by stating that he has things that need looking into, and that he had enjoyed talking with Frey.
After the date scene, Frey will come across Kiel talking to a Shady Merchant, who was inquiring about Arthur. Before Kiel could say anything, though, Forte comes along and drags Kiel away, lying by saying that Kiel had no idea who the merchant was asking about. Frey will then go talk to the merchant, who will begin to ask if she have heard of Arthur, identifying him as a well-known trader. The player can either respond by saying "Who?" or "I don't know who that is." In both situations, the merchant will back off and go ask others. This prompts Frey to go tell Arthur about the merchant. Arthur, however, seems completely cam about the situation, and says that he has things to look into before asking Frey if they could relay a message to Vishnal to "begin the operation."
The player will find Vishnal in the butler quarters at the castle. Vishnal appears to be busy, and the player can either choose "Sorry, is this a bad time?" or "Message from Arthur." (note: Arthur's name will be replaced by any pet name the player has chosen for him). Frey will relay the message, then ask what "the operation" is. Vishnal will admit that he has no idea what it is, only that he had been told to deliver a message to Forte.
Forte can be found back in Arthur's office for an unexplained reason (probably to notify him about the shady merchant), but before Frey can speak to Forte, Margaret comes in with food for Arthur, before beginning a rant about how Arthur should stop working so much and that it wouldn't kill him to eat with the rest of them. Her rant is cut off, however, when she realizes that Forte was there instead of Arthur. Soon after, Meg also realized that Forte had a "rude thought" about her. Forte accidentally reveals that she though Meg was acting impulsively and shrewish. Meg, of course, is less than happy to hear it and comes back by saying that she had written a song about Forte, but now she wouldn't to hear it. Their "conversation" ends abruptly when they see Frey standing there. Forte will ask what Frey was doing in Arthur's office, but Meg will point out that she and Arthur are dating, and is it so weird for her to want to see him? However, Frey states that she was not there to see Arthur, and had in fact come to deliver Arthur's message to Forte.
After reading the message, Forte will state that Arthur was in trouble and that she had to hurry. Frey will insist on joining her, and Forte gives in on the condition that Frey stay close (as if she couldn't handle herself). Forte will then temporarily join Frey's party, stating that Arthur was at the "Buried Cave" (the same one Arthur himself cites getting trapped in once during another sub-event).
Upon arriving at the cave, Frey and Forte will arrive to find Arthur and the shady merchant from earlier surrounded by monsters. After defeating the monsters, Arthur will explain what was going on.
Arthur had actually bought information about the cave from the merchant, who had said that the cave would collapse soon. This had been a lie, however, so when Arthur had planned on checking it out, the merchant had to "make it true" and took a hammer to the side of the cave. The sound had drawn some monsters in, hence why they were surrounded upon Frey and Forte's arrival. After the basic explaination, he will ask why Frey had come, and the player can either choose "Why wouldn't I?" or "...Please understand."
After that, the merchant goes on to explain his actions; supposedly, times were tough for those who tried to make an honest living...unless one was a merchant with great influence who could tell the people what the buy. He will then go on and blame Arthur and merchants like him for why his father's farm failed. Arthur, however, is comepletely unimpressed with his allegations and explains that merchants simply assess what the people want, and try to get desirable products out so that as many people as possible who want it can get it. He also pulls out a bag of tea--the same kind as what he had served Frey earlier. The "merchant" is suprised to learn that it came from his father's farm, and that Arthur was going to begin selling it, if he could. To finish it off, Arthur tells the wannabe that his father had asked him to tell his "good-for-nothing son" to "get his butt back home." Forte then leads the "merchant" off for questioning.
Arthur offers to take Frey back to town, and the scene shifts to the plaza. There, Arthur explains that he had everything under control, and that almost all of it had gone as planned...actually a bit better than planned. The player can then choose "I trust you" or "...Do you trust me?" In the case of the former, Frey will explain that she was worried, not suspicious. The "royal investigator" will be brought up, and then Arthur will explain that the "merchant" was the investigator...just not in the way everyone was thinking. After thanking and apologizing to Frey, Arthur will leave. The first half the event has been completed.