They have to wait a little while before they are dropped into place for their fight.
Both boys feel their minds sharpen quickly as they immediately begin looking for a visual on the Kaiju they need to take down codenamed 'Ironhide' for the armored plating it had on its body.
Tsuna isn't sure what it is, but something screams at him to 'turn left and duck' and Hibari who shares his mind and Tsuna react at the same time both boys and Jaeger turning as sharply as the Jaeger can manage while ducking down.
Ironhide lunges from the ocean water, mouth full of fangs snapping shut where their head would have been a moment earlier. Seconds later the Jaeger is holding the spiked tonfas Hibari had been so thrilled about and they're bringing one up and slam it into Ironhide's head, using the Kaiju's momentum against it. He crashes into the water and the two pilots tense in preparation for more.
Sure enough after a moment Ironhide rises out of the water and lunges at them again, his head sporting a small spot of blood right next to his eye where there was no armor and their spiked tonfa had caught him.
Hibari sees the attack coming, years of using tonfas telling him how to react, and Tsuna synchs up with him at the speed of thought (not to mention all the training they'd done together) so that they move at the same time.
One tonfa slammed under Ironhide's chin and lifts the Kaiju up just a little, his armor keeping the kaiju from coming completely out of the water as a smaller lighter opponent might have. Ironhide still lifts up enough for Hibari and Tsuna who have traded one tonfa out for the long dagger on their Jaeger, which they quickly shove up into the soft exposed section of Ironhide's neck where two armor plates meet. (Tsuna had spotted that weakness as soon as he saw the Kaiju. He was armored and it covered most of Ironhide, but there were places where there was no armor for movement purposes. Sucked for the Kaiju, good for them)
Ironhide roars in pain thrashing instinctively and making it worse for himself as the dagger is still inside his neck.
In the next few seconds the second tonfa is put away and the now free hand shifts into one of the plasma cannons Tsuna had cackled about. The shot is fired directly into the Kaiju's mouth where his roar cuts off sharply when Tsuna and Hibari continue to fire the cannon into the same spot (it takes some quick footwork and keen eyes, but they manage it) before they manage to shoot through Ironhide's mouth and head. Hibari almost snorts at Tsuna's sharp sarcastic thought of "Not so armor-plated on the inside are you?" (It had been a shock, finding out that Tsuna was sarcastic as sin inside his head, but Hibari had grown to appreciate the flash of sarcastic humor that usually showed up while Tsuna was fighting.)
It takes the boys a minute to realize they'd done it. They had beaten their First Kaiju.
They glance at each other and share a sharp grin.
"Good?" Tsuna asks silently.
"Fine" Hibari answers.
They get airlifted out and brought back to base shortly afterwards, both boys coming down off an adrenaline rush.