This series has just got the AXE. It ends on chapter 19 I believe. Just read the official twitter and manga authors accounts. This is an alarming trend when it comes to... certain types of Yuri. I hope that it's just a coincidence.
I stalked the author and manga's Twitter accounts and found nothing. There's a possibility I didn't search far enough though, so just in case, is there a source link for this?
I read up until chapter 19 (raws) as well. Slightly different from what conradin said, but (warning: spoilers from chapters after 14):
Essentially, over the last few chapters, Sena becomes more aware of the support she has around her. Most notably, she tells Kiku that at first, she disliked her and never wanted to see her again, but things are different now. From a previous chapter, Sena is worried over not knowing what love is. She also knows she can't keep Kiku waiting when it comes to deciding whether or not to continue their relationship. ALSO, it's kinda cute because Kiku repeatedly tells Sena she's willing to wait for her, but Sena knows despite what Kiku says, she's getting a little impatient (not in a bad way, lol).
Anyway, Sena eventually acknowledges Kiku as a comfortable presence in her life and tells her on her birthday that she wishes to continue this relationship with her as lovers, which makes Kiku cry, something that surprises them both.
I can't imagine the manga ending on chapter 19 nonetheless. Maybe a few chapters later, but also not likely imo.