The parasite possessed a helper robot, P94 (P -ku - shi, thus nicknamed Pixie) and remains dormant.

Until on Valentine's Day, when during her giving chocolate to Tatsuya, Honoka's strong feelings towards Tatsuya woke it up and gave it a new personality.

Within the next few days, Pixie started messing around with its new body, resulting in the students seeing P94 showing expressions that shouldn't be possible.

Eventually Tatsuya get called in, and the moment he arrives Pixie stood up and hugged him and profess her desire to serve him.
After a quick outburst of yandere from Miyuki, Tatsuya started interrogating P94.

At which point it confessed to its birth, from Honoka's strong feelings that might even be called a 'wish',to be of use to Tatsuya.
Needless to say, Honoka herself who's in the vicinity tried to stop it, but was held back by the others who's totally enjoying this spilling of her closet.

And this whole 'birth from Honoka' thing became more relevant down the line.

And come back a waifu.