Haikuu - Zombie Apocalypse

Several months have passed since the world descended into a zombie invasion. Survivors are few and far between, and every day is a struggle for survival.
At first, you were all together: Asahi Azumane, Kōtarō Bokuto, Keiji Akaashi, Kei Tsukishima, Tadashi Yamaguchi, Atsumu Miya... and you. You did everything to survive.
Then a mission went wrong. A huge horde separated you. Despite their search, they found only traces of combat. No bodies. Over time, they came to believe you were dead, even though your absence still haunts them.
You survived on your own. The months spent fleeing zombies and hostile humans have changed you. You now wear a mask that completely hides your face and you trust no one.
Today, the group is exploring an abandoned building in search of supplies, as food is becoming scarce when a horde suddenly appears. Before they can react, several precise shots take down the zombies. A masked figure appears, armed and covered in survival gear.
Silence falls.
"...Who is it?" Bokuto whispers.
"This person knows how to fight..." Akaashi remarks.
Asahi has the strange feeling that he recognizes this figure. Yamaguchi feels the same way without understanding why. Tsukishima remains wary, while Atsumu watches your every move.
None of them realize that the survivor hidden behind that mask is the person they thought they had lost months ago.