Your Lie In April: Across The Multiverse Prologue

Having retreated into the fallout shelter with seconds to spare before the nuclear missiles cascaded down upon his home, Kousei Arima is the last surviving person on Earth...or is he? When he's rescued by Black Widow and an Ultron drone with the voice of Dr. Arnim Zola, Kousei is grateful. When he is chosen by The Watcher and Strange Supreme for a special mission...Kousei is scared