My Hero Academia: Rise of Ben 10, Book 1.

The Bombing King

"Uhhhh.. guys?" The small grey alien with amphibious bulbous eyes with a black and white jumpsuit that looked like a cross between a gecko and frog humanoid peered out from inside the backpack with his large padded fingers. "Why are we doing this again?"

"N.. NO REASON!! J.. Just!" Izuku quickly adjusted the backpack in which the little alien was hiding. "Aizawa just established a new bonus credit project on how well people can spot contraband going into the school.. as a way for heroes in training to recognize hidden villainous activity.. just in case to be ready in situations like that.  We've been assigned the villain role, while the others have to spot you!"

"Really?" said the alien

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Present Mic: "GREY MATTER!!  Quirk: Small n' Smart! Agile, and fast,  this little 6 inch tall alien is agile and good at hiding plus getting into tight corners. What he lacks in power he makes up for in smarts. This guy has such amazing brain power that it can analyze and pick apart how a machine works just from looking at it briefly!!"

All Might: "Nezu theorizes that Grey Matter has an eidetic memory for every single thing Ben has ever seen or heard in his entire life, which means that things such as how to fix a motorcycle or complicated English Words that Ben might have even glanced over as a baby for 2 seconds are now perfectly recalled. But it may be more than that."

Present Mic: "WHO CARES how it happens, he's smart that's what matters!!"

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"Yes." Tenya answered this time. "And as diligent role players we must make sure we absolutely do our best to win!!"

Tenya and Izuku were walking to school with Kyoka and Ochaco. Ben none the wiser to the plot to possibly kidnap him by a mob and underground criminal, had been shoved into Izuku's backpack as Grey Matter after Kyoka, mere hours before, phoned Izuku and informed him Ben could use that.

"If anything, they'll be studying Ben's patterns." Izuku had said. "If he manages to come to school without anybody seeing him, then they'll never be able to pin down a route for ambush or anything.. for all they'll know, Ben's just teleporting to school or something."

"But then why don't we just use Ghostfreak?" Kyoka had asked. "Turn invisible and untouchable at the same time."

"There could be quirks that detect invisible people.. like heat sensing or scent." said Izuku. "Grey Matter is very small though, that means his scent won't be as prominent, and by using this method, we'll always be around to help.  Plus if there are heat tracking quirks or something similar, they'll be unable to detect him being so close to the body heat of whoever's wearing the backpack. "

"Only thing to do now is to figure out how to convince Ben to go along with this without letting him know what's going on." said Tenya. 

They hadn't told Kaminari, Bakugou, Mineta or any of the others in Class 1A, instead reserving themselves to telling Aizawa and All Might directly. 

In other words, other than the teachers, Izuku, Tenya, Ochaco, and Kyoka were the only ones who knew.. oh wait, yeah Gwen knew too. 

"The less who know about it, the less trouble we'll have." Aizawa had said. "We'll figure out something with Gwen on how to break the truth to Ben. You four just focus on keeping Ben's route to school secret for now, without alerting the enemy to our awareness of their plans."

So it had come to this. Aizawa had indeed put out the fake assignment to help sell it, saying he had secretly selected some students to smuggle a mystery item into the school, and it was up to everyone else to work together to figure out who was doing the smuggling, and what was being smuggled.