Luca smiled at Ayana's confession. He felt like he could see the gear in Ayana's head moving. He actually knew about Ayana and Sora meeting. He just wants to know whether Ayana had trusted him to tell him about Sora or not. To be honest, he was greatly disappointed when Ayana tried to keep it a secret, but he was glad that Ayana then started to explain the outline of her and Sora's meeting.
Let's take one tiny step at a time. She would open up to me when the time was right. Luca thought and didn't push her further. But then, Ayana confessed. He was surprised and was dumbfounded for a minute.
Before coming to Ayana school to fetch Ayana, he actually went to Canara laboratory. He went there to meet Sora and inspect the place. He also wanted to check on Sora. Although the thought of meeting Sora was gone when he also realized Ayana's presence in that place. his thought directly goes to Sora. Ayana must come here to meet Sora.