I believe in being truthful with children, but hopefully Kagome won't tell Rin the whole truth.  To tell her that her dad was a one- night stand that she doesn't remember the name of might be a little bit much.  Now is Kagome going to try to find Sesshoumaru?  Or is she going to marry someone else just so Rin can have a father?  I like the beginning of your story.  I can't wait for more! 

Oooh, I loved it!  And I don't think short chapters are necessarily a bad thing.  I think it goes with the beautiful simplicity of your story.  It is not cluttered, just enough words to convey your ideas, and draw a mental picture for your readers.  This is a rare gift.  I admit, I love long stories and long chapters, but it seems to me, since Kagome is a very young mother, and the story so far is about her and her very young daughter, simple language and short chapters feels just right.  You pointed out that Kagome was so young and naive that she didn't think she would get pregnant on the first try, and then in chapter two, when you described how she and Rin looked as they worked around the grounds of the shrine, reinforce that feeling of youth and freshness.  Even the colors you chose for their sundresses added to that feeling.  I hope you can write more soon, this is just the kind of story I enjoy reading, and you are doing it so very well... 

Sweeeeet!!!!!