Hey guys author here! If you didn't get what I mean at the end, I meant that Sana said those few words twice. She said it two times, meaning different things. 
“I'm sorry, I love you.” Means that she's sorry she can't spend more time with Tzuyu and she says she loves Tzuyu.
“I'm sorry I loved you.” Means that Sana is sorry she had to even love Tzuyu in the first place, as now Sana is dead and Tzuyu is left alone. 
It's two different meanings and it breaks my heart when someone says “I'm sorry I loved you.” It's just so sad ;-; if I made you cry, I'm sorry. I almost made myself cry with that ending. 
I might make a sequel on Namo, but a diff story. Like the next story would be on Nayeon trying to make Momo remember her. :) tell me if u want me to make that story! I hope you liked this Satzu Fluff and a bit of Angst at the end! I love Satzu and Namo but if you have ideas for me to write pls feel free to say! :) thanks again for reading!