LeanScript

local RunService = game:GetService("RunService")

local UP = Vector3.new(0, 1, 0)
local ZERO = Vector3.new()

local character = script.Parent
    local root = character:WaitForChild("HumanoidRootPart")
    local torso = character:WaitForChild("Torso")
    local rootJoint = root:WaitForChild("RootJoint")
    local leftHip = torso:WaitForChild("Left Hip")
    local rightHip = torso:WaitForChild("Right Hip")
    local humanoid = character:WaitForChild("Humanoid")

local LEAN_ANGLE = 0.3
local LERP_STRENGTH = 0.2

local cache = {
    root = {
        C0 = rootJoint.C0 - rootJoint.C0.Position,
        C1 = rootJoint.C1 - rootJoint.C1.Position
    },
    leftHip = {
        C0 = leftHip.C0 - leftHip.C0.Position,
        C1 = leftHip.C1 - leftHip.C1.Position
    },
    rightHip = {
        C0 = rightHip.C0 - rightHip.C0.Position,
        C1 = rightHip.C1 - rightHip.C1.Position
    }
}

local rootOffset = CFrame.new()
local leftHipOffset = CFrame.new()
local rightHipOffset = CFrame.new()
RunService.Stepped:Connect(function()
    local newDirection = humanoid.MoveDirection

    local newRootOffset = CFrame.new()
    local newLeftHipOffset = CFrame.new()
    local newRightHipOffset = CFrame.new()
    if newDirection ~= ZERO then
        local relativeDirection = (root.CFrame - root.Position):Inverse() * newDirection

        local axis = relativeDirection:Cross(UP)
        newRootOffset = cache.root.C1:Inverse()
            * CFrame.fromAxisAngle(axis, -LEAN_ANGLE)
            * cache.root.C0
        newLeftHipOffset = cache.leftHip.C1:Inverse()
            * CFrame.fromAxisAngle(axis, LEAN_ANGLE)
            * cache.leftHip.C0
        newRightHipOffset = cache.rightHip.C1:Inverse()
            * CFrame.fromAxisAngle(axis, LEAN_ANGLE)
            * cache.rightHip.C0
    end

    rootOffset = rootOffset:Lerp(newRootOffset, LERP_STRENGTH)
    leftHipOffset = leftHipOffset:Lerp(newLeftHipOffset, LERP_STRENGTH)
    rightHipOffset = rightHipOffset:Lerp(newRightHipOffset, LERP_STRENGTH)

    rootJoint.Transform *= rootOffset
    leftHip.Transform *= leftHipOffset
    rightHip.Transform *= rightHipOffset
end)