Nailed it. One of the pixiv tags is "最終兵器うつほ" (Saishuu Heiki Utsuho.)
In addition: The description seems to be something loosely like "I want to protect you with these arms." (あなたをまもる腕がほしい) The author mentions something about it (the previous quote,maybe) being from 進化論 (Evolution Theory...?) and how they were inspired to draw this based on it. I have no idea how the two relate, though.
Skribulous said: One of Saikano's main themes, basically (to protect their loved ones).
Ah. I meant the "Evolution theory" part in relation to the quote, actually (since the artist said they got it from there/were inspired by it.) I sort of assumed that it was a theme of the series just from what little I knew of it. Sorry for not being more clear.