Ever since Avengers: Age of Ultron introduced both Vision (Paul Bettany) and Scarlet Witch (Elizabeth Olsen), the MCU movies have been moving towards a comic book arc where these two characters become romantically involved. We saw a video from the Avengers: Infinity War set that featured a humanized Vision kissing Scarlet Witch, and now both actors confirmed in an on-set interview that their characters are "very much in love at this point," according to Paul Bettany, with Elizabeth Olsen adding that they are "soulmates." Paul Bettany adds that this relationship helps him understand humanity.
"I think that Vision's been on this quest to understand what being human is and I think Scarlet Witch [has] in a large degree helped him figure that out and what love is."
Fans saw their relationship start to grow in Captain America: Civil War, but many have been wondering about that set video ever since it was posted. While Vision isn't human on a biological level, Bettany reveals that the character has learned he has the ability to change his appearance with nano-technology, which he uses to make himself more human to go on undercover missions with Captain America (Chris Evans). Elizabeth Olsen also revealed that, like Captain America: Civil War, each character has their own arc, and her arc for Scarlet Witch is the most "emotional" for her.
"I think in a different way not so much about the last movie and their own sagas, but this is definitely the most emotional arc I've done in an Avenger film, that's for sure. Because when we're talking about Vision becoming human, we're talking about their relationship and it's a pretty grounded arc."
Even though he can disguise himself as a human, Vision's Mind Stone that gave him life, which is embedded into his forehead, is still visible. Since the Mind Stone is one of the six Infinity Stones that Thanos is seeking, Vision will be a target of the Mad Titan at some point in the story, and while Thanos has been seen wielding the Space Stone and the Reality Stone in Avengers: Infinity War footage, we haven't seen him with the yellow Mind Stone yet. Paul Bettany further stated this about Vision and Scarlet Witch's emotional arc through Avengers: Infinity War.
"Yeah, I think it is the most emotional. Also, the cost and the danger that we're all facing becomes more important than certain beef that people had in the past because it's so desperate. The point of the Avengers, and by extension mankind, it's fraught with danger. So I think old grudges are buried and put off until next time."
These interviews were conducted on the Avengers: Infinity War set last summer, with ComicBook.com reporting that the scene they watched being filmed took place in Wakanda, with one of the two characters already "seriously injured" upon arrival in the African nation, although it wasn't stated if Scarlet Witch is injured, or if it is Vision. With almost exactly one month left until Avengers: Infinity War hits theaters, we'll find out more about these characters soon enough.