(A/N: play vid if you wanna! <3)
Frisk's P.O.V.
*KACHOOOOW*
    I woke up to the sound of thunder. I jumped up and started crying. I felt two hands wrap around me, trying to comfort me.
    "Woah kid, you okay?" Sans asked me. I just kept crying. Ever since Aidan died, I hated thunderstorms.
    I nodded my head while tears ran down my face. Undyne was still asleep, and the other fort was silent. Sans and I were the only ones awake.
    "Uh...heh...you don't seem okay," Sans said, hugging me tighter. "What's goin' on?"
    I took a deep breath. I...always get scared when I talk about Aidan's death. Usually more tears come. This always hurts...whelp. This is gonna suck.
    "I get scared of thunderstorms b-because," I said, voice shaking. "It reminds me of...A-Aidan."
    Sans looked at me, confused. I took another deep breath while wiping away tears.
    "Back on the surface," I explained to Sans, shivering, "I had an older brother. Aidan. He was the one who kept me going. The one who loved me to death. The one who...protected my sorry ass."
    "O-one night," I said, more tears streaming down my face and voice shaking, "My 'Foster Dad' came into our room, holding a gun. A shot rang out. I-I saw my brother...o-on the ground...his last w-words were: 'I l-love you.' And I didn't even get to say 'I love you' back, because before I knew it...he was g-gone."
    "T-that's why I'm s-scared of thunder. It reminds me of...the gun s-shot..." I finally said. It felt good and bad to get it out. I felt Sans' teeth press against my head. I sobbed.
    "S-sorry...I-I--" I tried telling Sans, but interrupted.
    "No. Stop, that's rough, Frisk." Sans told me, his hands running through my hair. "I totally understand. Heh, you have no idea how I'd be without Papyrus."
    I closed my eyes, feeling safe in his arms. I smirked a little. Sans sang me a lullaby, which instantly got me to sleep.

"A gentle breeze from Hushaby Mountain,
Softly blows o'er lullaby bay...
It fills the sails of boats that are waiting--
Waiting to sail your worries away.
It isn't far from Hushaby Mountain, and your boat waits down by the quay...
The winds of night so softly are singing,
Soon they will fly your troubles to sea...
So close your eyes on Hushaby Mountain,
Wave goodbye to cares of the day.
And watch your boat from Hushaby Mountain,
Sail far away from lullaby bay."

(A/N: I know this chapter was a bit short, sorry for that!! But I'll update later on today!! The Undyne Undyne promises you!! <3 <3)