I thought that I thought that I could write it finely, I thought that the replacement core of 0.38 and 0.5 does not correspond. Also, although it is a personal opinion, it is not a knock expression, so it is not suitable for a young girl (troublesome)
I bought 0.4 because the ink of 0.5 disappeared. From 0.5, the ink is moderate and you can write very fine letters. You can write kanji with a large number of strokes without collapsing. Even when rubbing and erasing characters, it disappears and disappears as close to perfection.