Board Thread:Wiki/@comment-30049797-20160924003216/@comment-1327106-20170825171553

Insieme wrote:

Manuel de la Fuente wrote: However, the complaint may be valid. It's true that the official Kodansha USA translation of the guidebook says "adopted" (twice), but I just checked the original Japanese version and it contains the kanji for "引き取る" (Hikitora), which doesn't mean "adopted" but "taken in". It seems that "引き取る" (Hikitoru) also means "to adopt". Check it out. Manuel de la Fuente wrote: Ok, so it's been two days after this, and although I asked in several sites, there are no Japanese arguments against the use of "adopted", so we stick with Kodansha USA translation. The wiki's stance is that they are adopted siblings. This debate ended last year and it was regarding how Mikasa is called Eren's adopted sister on the wiki. Any attempt to remove her status as adopted sister in AoT wiki articles will be reverted.

Individuals are free consider them as "just friends" as much as they want.

Arguing whether Mikasa was taken in or versus adoption with legal paperwork is splitting hairs. We do not know how the society within the walls handles adoption. It is entirely possible that it's as simple as taking in another kid, and not every adopted child in the real world takes on their adopted parents surname, especially if they're older.

In the anime you can hear Mikasa refer to Eren as "family" (kazoku), which I think implies that she considers their relationship a familial one. You don't say that of a good friend or your boyfriend.