@BzzBzz
are you refering to jap or english? because in english "in-law" is never used for adoptive relationships and would be a translation error if used this way. adoptive parent/mother/father is just adoptive parent/mother/father.
@BzzBzz
An in-law of any gender or age is someone who is related to you by marriage they are your spouse family who became your family via your marriage to your spouse (like how Risu's father mother and brother will become Fulio's father-in-law mother-in-law and brother-in-law)
Uh, TIL english makes the difference between the two
We only have one "word" for both of those case in french : "belle mère" (literally good looking mother)
Now to wonder why