Well, Blake picks up the Notebook, and things get interesting from there.

"She's right here!" Jaune said, grabbing Velvet's hand, making her squeak, and pulled it to Ria... Where it went through her abdomen. "...Okay, what the fuck?" he asked.

"Ah, I'm also intangible to those who can't see me, though I can control it for those who can," Ria cooed, grabbing Jaune's hands and pulling them to her supple boobs. She cooed as he instinctively squeezed. "They feel great, don't they?"

"Ye- yeah..." he said, blushing, pulling his hands back once Ria released them.

"Master?" Blake asked, still concerned.

"...maybe he's hallucinating?" Velvet asked. "He DID just hit his head..."

"I'm not hallucinating!" Jaune protested, trying to think of a way to handle this downright bizarre situation.

"That can't be it," Blake shook her head. "He hit his head AFTER he started seeing things. That also doesn't explain what happened to Ms. Goodwitch..."

"...maybe check the Note?" Velvet asked.

"Good idea," Blake acknowledged, causing Ria to smirk deviously as Blake bent down to pick up the Note. She straightened up, and looked back at Jaune...

"...3...2...1...," Ria counted down in amused tone.

"What the hell?" Blake asked, staring at Ria.

"Wait, you can see her now?" Jaune asked, surprised.

"Apparently... I still don't get what's- Mpph!" she yelped as Ria glomped her neck, petting her cat ears as she pet Blake's head.

"Aren't you so cuuuuute?" Ria squeed a bit. "I just love cat girls!" Blake meanwhile flailed as she fought for air.

"You too Blake?" Velvet asked fearfully, looking around as if afraid she was next.

"Hey, please let her go," Jaune asked Ria.

"Alright," she agreed after a moment, releasing Blake, who started gasping.

"Okay..." she panted. "You're definitely real... But how come only Jaune and I can see you? And why did Jaune see you first?"

"Blake?" Velvet whimpered.

"I thought it was kinda obvious," Ria shrugged. "Guess."