Okay, first the serious stuff. See? This is why I hate idiots in manga (in general, not specifically this one) going "dense MC" this or "beta cuck" that. The dude is perfectly valid.
She keeps showing him her panties like it's a joke. Keeps teasing him like he's a joke. Gets close and personal with just about anyone (poor Mori-kun).
What part of that suggests "I like you" to any of you guys?
And now the important part. Did nobody notice the tennis players? They're the same girls that are always walking in on them. They literally felt the disturbance in the Force 😂
Edit: Okay, my bad, I went back to check and they're not the same girls. Sad. But still.