All of it

"What's the worst that could happen?" Ruruka shrugged as she started to pour all of the bottle's contents into Seiko's food before stirring the food around so it mixed in with every bite of the food.

Ruruka then put the lunch box back where she found it before finding a place to hide as she waited for Seiko.

After a few minutes, Seiko returned and sat back at her desk.

'Come on...' Ruruka thought, waiting for Seiko to eat her lunch.

Eventually, she saw Seiko start to eat her lunch. After a few bites, Seiko put her hand to her head with her face displaying some form of discomfort.

'Okay, now to see if it worked.' Ruruka silently slid out of her hiding space and approached Seiko.

She put her hand on Seiko's shoulder. "Hey, are you alright?"