Eila Ilmatar Juutilainen (エイラ・イルマタル・ユーティライネン, Eira Irumataru Yūtirainen?) is a witch of the 501st Joint Fighter Wing, originating from Suomus and affiliated with the Suomus Air Force. She is referred to as "Illu" by her friends, and is sometimes named Diamond Ace. Her familiar is the black fox.
Eila's magic ability Foresight (未来予知, Mirai Yochi) grants her a limited ability to predict the future. Her hobby is fortune-telling with tarot cards, although the accuracy of her predictions is questionable at best. Similar to stereotypes of her familiar (the black fox), she has a reputation for mischief, being fond of pranks amongst her colleagues and is somewhat mischievous.
Eila is often partnered with 501st Night Witch Sanya V. Litvyak, and perhaps as a result (perhaps it is simply chemistry) the two have become very close; Eila is often portrayed as fiercely protective of her younger squadmate and takes on a sometimes awkwardly nurturing role during down-time. Whether this interest is romantic or plain, big-sisterly fondness is up for interpretation.
Eila is based on the #1-ranked Finnish flying ace (and #1-ranked non-German flying ace) Eino Ilmari Juutilainen. Like Eila, he bore the nickname "Illu" amongst his friends. Her magic ability, Foresight, is a reference to Eino having never been hit by enemy fire.
She has an older sister, Aurora E. Juutilainen.