"Table Does Not Exist" Error from Recursive CTE Query Inside Function

create or replace database ck2;

use ck2;

create table Characters (

    id int unsigned key,

    mother_id int unsigned check (mother_id != id),

    foreign key (mother_id)

        references Characters(id)

        on delete cascade,

    real_father_id int unsigned check(real_father_id != id),

    foreign key (real_father_id)

        references Characters(id)

        on delete cascade

);

insert into Characters values

    (0, null, null),

    (1, 0, null),

    (2, 1, null)

;

create or replace function count_descendants(cid int unsigned) returns int unsigned return (

    with recursive Descendants as (

        select * from Characters where id = cid

        union

        select c.* from Characters as c, Descendants as d        

            where d.id = c.mother_id or d.id = c.real_father_id

    ) select count(distinct(id)) from Descendants

    );

select count_descendants(0);