This is an idea I have, imaging it more as an anime that's showing respect to the mecha and kaiju genre like Pacific Rim.

Imagine, if you will, the earth being hit by several meteors. Soon after, giant kaiju start appearing and rampaging across the world. A young boy named Arthur discovers an a machine in the ocean, a machine able to fight back against the beasts. The Kaiju Buster.

For Arthur's appearance, imagine a younger version of Hetalia's America.

Kaiju Buster appearance is a mixture of Gypsy Danger, Eva01, and Gurren Lagann. Holding a blue and grey color pattern with the face mask being white. The eyes shine brightly with yellow and the helmet holding two yellow spikes in opposite directions. Also it stands at 70 meters tall.

Kaiju Busters Arsenal include: Twin plasma cannons from each hand, superheated blades that come from each arm, shoulders and legs holding an assortment of missiles, and the chest holding the most powerful weapon, the Atomic Breaker Cannon.

Berserk: Kaiju Busters face mask opens up and goes on a brutal rampage, never stopping until the kaiju is completely eradicated.

Kaiju Buster has an incredible ability to absorb the abilities of each kaiju it defeats, holding it into its Grid to be used for different occurrences.

While I have not thought of every kaiju to fight, here's a few.

ThunderLord

A 70 meter tall reptile who's a reference to Godzilla. Reptilian in appearance, it sports a color pallet of red and yellow in the shape of lighting. Yellow blades litter it's back as conduits. It's head is a mixture of a crocodile and monitor lizards. Its main ability is to produce a beam of electricity by means of an conduit organ in its chest. The beam is able to shoot fast and able to slice through buildings with ease.

Ability: Thunder Cannon

The Atomic Breaker Cannon is supercharged and is able to get charged by electricity. The beams destructive capabilities increases tenfold when using the Thunder Cannon.

Armipede

Originally starting out as a horde of 9ft tall insects with appearances similar to rhinoceros beetles. Thousands of these insects swarm the skies and find any source of energy to feast on.

When the threat is high enough, the swarm will combine into a 100 meter long centipede creature. The energy they absorb turn into large plasma blades that can cut through almost anything. This kaiju is a reference to Legion from the Gamera franchise.

Ability: Plasma Blades

Kaiju Buster is able to pull from the Grid two handles that erupt into curved energy blades.

Seraphim

A 50 meter ball of light that slowly travels around the sky. It's light is almost blinding to look at, acting as a miniature star. When attacking, it takes shape of a six winged figure with a giant eye in the center. It's ability is to shoot an immensely powerful laser and hold onto the beam for a long period of times. This is a reference to Ramiel from Evangelion.

Ability: Spear of Retribution

Kaiju Buster is able to pull from his Grid a giant golden spear. No matter how far it is thrown, the spear with always return to him to be wielded again.

Mecha-Thunderlord

It's essentially a robotic version of ThunderLord, complete with an entirely new arsenal of bombs, lasers, and blades. An electric core boosts its lightning breath immensely. This is a reference to Mecha-Godzilla.

Ability: Thunder Armor

Kaiju Buster is able to pull from his Grid separate parts of Mecha-ThunderLord and place them on itself. Acting as extra armor and firepower for those special occasions.