Noelle Silva is one of the most important main characters in Black Clover. She's an emotionally guarded girl, protecting herself from hurt and ridicule by presenting an arrogant attitude to everyone around her. But this is due to not only her royal status, but also the fact that her family has treated her like an outcast since birth because of her inability to control her powers.
When she was rejected by her brother Nozel's Magic Knight squad, the Silver Eagles, she was recruited by Captain Yami Sukehiro into the Black Bulls at the same time as main character Asta. Noelle is clearly disdainful of Asta at first, showing him her especially rude side. But Noelle Silva is keeping a huge secret: she is in love with Asta. And it's time she told him the truth -here's why.
Initially unimpressed by Asta's loud and excitable personality - not to mention his low social status - Noelle harshly rejects his attempts at friendship at the beginning of their relationship as teammates. But, after fighting alongside him on their first mission in the Sosshi village, seeing his willingness to sacrifice himself for the safety of others and his continuous support and encouragement of her training to control her water magic, Asta's charms began to take effect. Even more so when he came to Noelle's defense when her siblings derided her for "shaming the family name" by not being a powerful wizard. Asta's willingness to be friendly to and stand up for someone who didn't even like him led to Noelle eventually developing strong romantic feelings for him.
Now, Noelle is deeply attached to Asta. Her feelings often manifest in the form of jealousy, like when Mimosa admitted her romantic feelings for Asta, or helpfulness like how she gives him water to drink any time he's thirsty. But, although Noelle has acknowledged her feelings to herself, she is still shy and insecure. She goes out of her way to hide her emotions by blasting him with water whenever he gets too close or makes her uncomfortable, picking arguments with him in an attempt to deflect his attention from how she truly feels.
Noelle admitting her feelings for Asta would be amazing for each characters' emotional arc. They would each likely grow and mature as people, becoming more emotionally stable and confident in their own powers as their relationship grows. Noelle could be Asta's magical anchor, merging her mana with his anti-magic to boost both of their abilities. It would also be fun to watch two such explosive personalities navigate being in a committed relationship.
Although it is impossible to tell when or if she will ever confess her love to Asta, one thing is certain: Noelle Silva and Asta, the future Wizard King, are the power couple that Black Clover needs.