Well, we all can accept the fact the both Fuwa and Yua were the best Rider combis. Both the actors coincidentally had a common thing among them. That is both the actors are alumni of Waseda University. Though there were a lot of disruption and difference between their combi as characters, they will always be grouped together.
Mantan Web had recently interviewed Ryutaro Okada (Isamu Fuwa / Kamen Rider Vulcan) & Hiroe Igeta (Yua Yaiba / Kamen Rider Valkyrie) for Kamen Rider Zero-One the Movie: REAL×TIME and both of them have revealed the first impressions of each other.
Here's what Hiroe Igeta had mentioned about Ryutaro Okada. "I was initially excited to know that we are from the same university. I had a impression of "Funny Big Brother with Kansai dialect" about him". As the filming continued "Okada-san had a part of Fuwa in him. In end, he became a hot Big Brother with Kansai dialect". She also reveals that "He doesn't emit too much of his Big Brother side" during the filming. "Even if there was a scene where Yua says something serious to Fuwa, he talks with me at the equal level and frankly once the cut comes. That is also not like a Sempai. Due to that I was able to say something seriously as Yua". To this Ryutaro-san had said "I had never thought about it (talking at equal level) at all".
Now coming to Ryutaro-san's impression of Hiroe-chan "She has more of a Big Sister like feel. More than me, she leads during filming. Hence in that sense there is no elder of younger in terms of age. Hiroe-san has innocence in her and her smile is also sweet compared to Yua who is a little unfriendly. The gap is amazing. I also have impressions that Yua had some feel of Hiroe-san from the middle"