Letters (Niall love story)

About a week after the weird call with Niall, I was walking up the steps to the flat Matt and I shared, and I noticed a note on our mailbox. It was from the postal office, saying that they had tried to deliver a package but no one was home. I groaned as I turned around and headed back to my car, getting in and turning the heater on. I drove to the post office, parking close to the front and heading inside.

About ten minutes later, I came back out with the package. I had noticed that the home address was Niall's in London. When I got back in my car and turned the heat on, I reached for the package and ripped it open, curiosity getting the best of me. A bunch of envelopes and a note fell out on my lap. I picked up the note, and read,

Kara,
Please read the enclosed letters in the order they are marked in. Try to read one each day or two a day. Don't show them to Matt. I hope these letters will clear up some things for you and maybe take this weight off of my shoulders. Please try not to let this affect our friendship if you don't feel the same.
Love,
Niall

What did he mean, "don't feel the same?" After rereading the note several times, I picked up the letter marked "1", opened it, and began to read. After a few lines, my eyes widened and I let out a little gasp.

Notes