He Who Fights with Monsters · Character
Colin
Also known as Leechy, Sanguine Horror, Team Colin
- Supporting
- First seen · Book 1 · Ch. 27
At first glance, Colin is little more than a leech; then the shape gathers and multiplies into something impossible to ignore. Its slow, undulating movement and tooth-lined mouth make even its silence feel hungry.
- Gender
- male
- First appears
- Book 1 · Ch. 27
- Books
- 3
Colin begins in Book 1 as Jason Asano’s unsettling leech familiar, a blood-swarm weapon that merges with his summoner’s veins and provides both healing and battlefield utility. By Book 10, the familiar has awakened multiple forms—blood-red humanoid, swarm, and monstrous shapes—becoming a Voice of the Will whose shifting biomass reflects Jason’s growing divine nature. In Book 11, Colin fully embodies Jason’s likeness, speaking with his voice and serving as a living vessel that safeguards the mortal aspect of his creator during the final ascension, transforming from grotesque parasite to indispensable companion and mirror of Jason’s identity.
Description
Colin has no human body or clothing, appearing instead as a slick leech or a dense, shifting pile of them. In its larger form, the mass can exceed Jason’s body volume, its dark wet surface slowly rippling as the creatures move together. Their mouths bristle with blood-sucking, lamprey-like teeth, giving the swarm a single monstrous maw when the forms bunch close. It can also reduce itself to one small leech, an incongruously quiet presence when perched on a shoulder or crawling across a hand. Colin has no one fixed appearance: his forms include a blood-red humanoid figure with Jason Asano’s shape, ember-red eyes glowing in an otherwise dark void, and a rust-red robe. He can also appear as a writhing swarm or pile of leeches with teeth, with other monstrous forms marked by features such as eight arms, shark teeth, and eye-shaped mouths. His overall impression is organic, uncanny, and difficult to mistake for an ordinary person. Colin’s body is a glossy, glistening mass of crimson blood, shaped into a replica of Jason Asano. His eyes shine like red orbs, and divine markings are etched across his body; his face can become smooth, featureless skin, erasing the familiar human arrangement of features. His substance suggests a leech-and-lamprey horror, with a wet, polished surface rather than ordinary skin. A starlight cloak is associated with his airborne form, completing an eerie silhouette that feels both Jason-like and profoundly inhuman.
Connections
Family & partnersFriends & mentorsRivals

Jason Asanoconflicting source relationships
Begins as a magical summoner-familiar link in Book 1; evolves into a close, playful partnership by Book 10 where Colin is treated as a companion and equal; by Book 11 the bond deepens into an almost fraternal relationship, with Colin acting as both protector and living reflection of Jason’s identity during his ascension.
Story so far
BOOK 1He Who Fights with Monsters: A LitRPG Adventure
- Obtained as Sanguine Horror familiar during Jason’s apocalypse awakening
- Merges into Jason’s bloodstream, healing wounds from the summoning ritual
- Manifests as either a single leech or a massive swarm that infiltrates armored foes
- Rests on Jason’s shoulder or hand before dissolving back into his blood
BOOK 10He Who Fights with Monsters 10: A LitRPG Adventure
- Awakens multiple stable forms instead of a single body
- Becomes a Voice of the Will, gaining access to many of Jason’s abilities
- Transforms by spending and rearranging stored biomass
- Coordinates with Jason in battle as an equal partner
BOOK 11He Who Fights with Monsters 11: A LitRPG Adventure
- Assumes Jason’s exact shape and speaks in his voice
- Dissolves into blood mist and reforms at will
- Displays divine patterns on blank skin as Jason’s nature changes
- Preserves Jason’s mortal aspect in his body while Jason ascends
- Reunites joyfully with Jason after helping reach him during his lost state
Appearances
Meet Colin in Bookworm
Meet Colin in your EPUB — spoiler-safe to the book you're on.


