It has a stylish, ninja-like appearance based in blue, with a long pink tongue wrapped around its neck like a muffler. Following Samurott, the Water starter of the previous generation who was based on a samurai, this design continues the theme of ninjas and Japanese elements. Its body color is a tight navy blue, and though hard to see because of it, it does have nostrils. The white circular parts on its elbows and knees are remnants of the bubbles from its pre-evolved forms, Froakie and Frogadier. With its slender body and prominent webbing between its fingers, its motif is a gliding frog. Its name comes from the frog's croak "Geko" and the "Koga-ryu," one of the most famous schools of ninjutsu. There is also a theory that it relates to "Gekko" (moonlight) due to its nocturnal nature. Its greatest feature is the ability to secrete a special mucus from various parts of its body that can harden water to the strength of metal. In battle, it places its hands on the cross patterns on its thighs to generate shuriken or ninja blades made of water, engaging in versatile combat. Their sharpness is enough to easily slice through real steel (though weapons other than shuriken tend to be shown more in other media). Its tongue muffler serves as a sensor to detect the movements of unseen enemies by feeling air currents. In emergencies, it can unwrap it to use as a freely moving wire or weapon. While it is a Pokemon with a very sharp appearance and fighting style, it generally has a peaceful temperament and dislikes unnecessary conflict. In the games, its default expression when not in battle is the same relaxed, squinty-eyed look it had as Froakie and Frogadier. It dislikes having the white parts of its limbs touched, but its face turns into (＞＜) with joy when its tongue muffler is petted. Cry: "Geko" "Koga" "Greninja"

The form of the Ninja Pokemon, Greninja, after Mega Evolution. In this form, its torso, thighs, forearms, and head are unified in a deep black resembling ninja attire, and the area around its eyes changes into a sharp light-blue shape resembling a Water Shuriken. Additionally, small Water Shurikens are equipped on both thighs, allowing them to be thrown instantly as needed. The biggest difference is a giant Water Shuriken made of gel-like mucus that floats and rotates at high speed like a drone; the main body clings to it in a handstand position. While the opponent is distracted by this flashy posture, it wraps its long tongue around them to bind their movements, then charges in with the giant shuriken to finish them off. Its reflexes have been drastically enhanced by the release of energy from Mega Evolution. To maximize this advantage, it has shifted to a style of "being a ninja but not hiding," intentionally exposing itself to draw the opponent's attention. It induces attacks, senses the slightest presence, and counters faster than the opponent. For Greninja, whose creed is to be elusive like a ninja, showing this form—which discards that stealth—is a signal that it is going for the finish, a declaration that it has entered the range of certain victory. Cry: "Geko" "Koga" "Greninja"

The evolution of the Kalos Water starter, Froakie. It has grown taller and sleeker, characterized by its blue hole-punched hands, blue-tipped feet, and a face that looks like it's wearing a blue mask. Like its time as Froakie, it is equipped with a bubble muffler. With limbs that can stick even to vertical walls and its natural agility, it possesses the formidable ability to scale a 600-meter building in just one minute. It also has the control to hit an empty can 30 meters away with a pebble wrapped in bubbles, showing glimpses of the Greninja it will become. Cry: "Geko" "Gashira"

It has the appearance of a frog with a light blue body and a white fur-like wrap. Its name likely comes from "Kero Kero" (a frog's croak) and "Utakata" (bubbles/foam). Including its evolved forms, it makes a squinty-eyed face in Pokemon Amie and the anime. Many people find this squinty-eyed state cute and it is well-received. While it appears to have a laid-back personality, it is actually a calculating and theatrical Pokemon. It lowers the guard of those around it with its carefree demeanor while always keeping a sharp eye on its surroundings. As soon as an enemy shows an opening, it reverses its attitude and overwhelms them with blinding speed. It fights using its natural, extraordinary jumping power and tactics involving bubbles. Perhaps as a hint of its final evolution, Greninja, many of its move motions are somewhat ninja-like. The white parts are a special foam called "Frubbles," secreted from its back and chest. It has a springy, delicate texture and serves to protect its skin, which is sensitive to drying out. At the same time, it has strong elasticity and some stickiness, which is useful in battle for blinding enemies by launching it at their faces or absorbing attacks to reduce damage. Cry: "Kero"