In written or printed hiragana, a small circle at the end of a statement is equivalent to a period ?
I already know the " mark after a Hiragana character changes the original sound of that character. For example. Ka changes to ga

Question

Answer

Yes, i think it is if you refer to "。".

Answer

As you say  "ka"   Like ~ desuKa  terminate sentence  (question sentence )   marked "。”　but If
~Ga　　Tomodachi Ga  this is one phase complete use "、“　We make difference. In rule of Japanese sentence If terminate the sentence  One letter space or make spaceing or terminate mark "。”　(Maru as read) as like period (dot) but middle of sentence one phase or one parts phase of sentence do not have to marked "," (Ten as read) but it marked the reader easy to understand one phase end. so not alway "Ga" marked "、”　Now use "?" mark "!" mark in Japanese sentence for understanding for others but it is not rule. It just mark for Undersatnding Please note.