Labeled 「双魔神」(「そうまじん」?; Sou-Majin; Twin Demon Gods) in Issun's scrolls, Lechku and Nechku are two demonic, menacing owls whose body are composed of mechanical clockworks, and other body parts based on the same theme. Lechku's body is an analog clock with Roman numbers, while Nechku's is a clock with flipping pieces bearing old numerical kanji (大字 daiji) from zero to nine on three slots, and above this clock is a decoration piece of a night sky with a crescent moon and stars, fitting for Nechku's description in its Bestiary entry . Under the clocks are a mass of cogwheels and mechanisms, and hidden underneath these are the deadly talons with razor claws, usually pulled up behind the mechanisms. Atop the clocks, the arms of Lechku and Nechku are present, scrawny but also riddled with muscle, and are small and short compared to their bodies. On the side of their bodies, under their toga are owl wings, enabling them the ability of flight. Their heads are one of the most noticeable features, each demon with an eye of the demon's color, the other has a monocle over it. On the side of each demon's head is a turning gear used to externally control the mechanisms in the demon's body, and in the Ōkami Official Complete Works, Lechku and Nechku are shown to turn these gears at times. Nechku also has a mustache above its beak, and coupled with the top hat each demon has and the cane they hold, Lechku and Nechku are given a formal and Western gentleman-like appearance.
The twin demons were originally altar statues on the twin peaks of Ezofuji. However, one day, they came to life and attacked all of Kamui. A brave Oina hero defeated them, and they returned to their statue state. However, 100 years later, they returned and used the Blizzard machine to bring unending winter to Kamui. They then injured the Oina elder, Kemu, preventing him from performing the annual Volcanic Incantation to end the winter. They also abducted the one other Oina with the ability to perform the Incantation, Lika, and sent her through the Spirit Gate to be eaten by True Orochi.
After rescuing Lika, Oki and Amaterasu infiltrate the Wawku Shrine to defeat the two demons. Amaterasu finds Nechku and her past self, Shiranui, also steps in to help. Their combined might is too much for the demon owl. However, upon Nechku's defeat, Lechku appears and heals its opposite. The two wolves prepare to fight Lechku, but Oki rushes in. Determined to defeat the demons, he attacks them. However, the demons then use their trump card: They freeze time, allowing them to attack Oki easily. However, as the demons prepare to deliver the killing blow, Shiranui jumps in and takes the blow, severely injuring himself. While Oki and Amaterasu tend to Shiranui, the twin demons escape to another altar in the shrine.
Oki and Amaterasu eventually find and kill the demons, but now fight them as a team. The twins fight the duo to the best of their abilities, but are no match for their teamwork and the combination of Amaterasu's awakened power and the awakened power of the sword Kutone. Dying, the crumbling owl demons crash into each other and explode in a blast of light; lifting the burden on Kamui.
The first battle with Nechku is simple enough, as all Amaterasu has to do is dodge any attacks aimed at her and watch Shiranui's superior powers deal with the demons. Amaterasu can also help out when Nechku has been knocked to the ground to end the fight more quickly.
Against Lechku & Nechku
The battle is straightforward: just dodge the demon's minor attacks and use specific Celestial Brush techniques when they summon objects out of their hats. The demons' attacks include swooping at Amaterasu and grabbing her before throwing her down, and a time-slowing attack in which they spin at devious speed. Oki is also attacking them, but he can only launch icicles at them, which bounce off their tough hides. Instead, Amaterasu must wait until one of the demons summons an object from their hat, which are a Giant Bud (use Bloom, provides Spirit Globes and Ink pots), the egg-like object the Spider Queen summons (Power Slash it like before to stun the owl which summons it), the cursed fruit Cursed Trees and Bud Ogres throw (Power Slash them back to stun the owl which summons it), Ninestrike (use Thunderstorm on it with the lightning in the sky above the battlefield to stun the owl which summons it) or a bomb (use Inferno on it to blow it up early and stun the owl which summons it). If the correct Celestial Brush techniques are not used, the owls will be able to damage Amaterasu with the summoned objects. When one of the demons has been stunned, Oki will make a bow around himself. Bite the bow and pull back, then release to fire him at the stunned demon, then use a Celestial Brush technique to draw it to the ground so that Amaterasu can attack it; otherwise they are invincible. Using any offensive Celestial Brush techniques on the demon that Oki is launched at will bring the demon completely to the ground immobilized, leaving them vulnerable to ground attacks. However, if Amaterasu uses a technique while the demon is knocked down, then its element must match that of the brushstroke she used to knock the demon down earlier (e.g if Icestorm/Blizzard is used to knock the demon down, then only the same techniques can be used to safely damage the demon), otherwise the demon will spring right up. Each demon has its own health bar, so both must be defeated to end the battle.
- Although the spirits of Lechku and Nechku go into the Ark of Yamato, and concept art shows they were meant to be fought in it, they are not on board the ark.
- The reason they are not on board is possibly because Oki is a key element in the battle against them, but implementing an element like that would take too much time.
- Another possible reason is because the game developers realized that players did not want to redo such a recent fight.
- An additional possibility is that Waka could have fought and killed them both on the way to face Yami.
- Lechku and Nechku are based on the demon passed down through Ainu traditions, Mosirecik-Kotanecik (「モシレチㇰコタネチㇰ」?), and splitting him into two demons was an original decision of Ōkami creators. In the Ainu mythology that involves him, the demon traps the Ainu sun goddess (Tokapcup-Kamuy, Ainu equivalent of Amaterasu), who is then rescued by Ainurakkur, an Ainu hero warrior. The demon is also described to have one eye "as big as the moon" and the other "as small as a [...] seed", which is visible in Lechku and Nechku's asymmetrical eye design.
- The owl shape and color motifs (gold and silver) of the altar statues Lechku and Nechku possessed are a reference to a protective Ainu owl-god Cikap-Kamuy, who sheds tears of gold and silver in the mythology.
- The titles of Gold Demon and Silver Demon may be also a reference to the two demon king brothers from the Chinese classic Journey to the West, also known as the Great King Kinkaku (「金角大王」?; Kinkaku-daiō) and the Great King Ginkaku (「銀角大王」?; Ginkaku-daiō). "Kin" (「金」?) and "gin" (「銀」?) mean "gold" and "silver", respectively.
- They personify the passing of time and the inevitability of all things coming to an end, as shown by the two styles of clock in their chests.
- These two are among the bosses in Ōkami who do not speak, along with Crimson Helm and Yami.
- The cutscene that plays after Lechku and Nechku are defeated varies, depending on the order in which the twin demons are defeated. Whoever is defeated last will crash into the other one, who was defeated first.