Why is katakana /va/ normally written ヴァ rather than ヷ?


Even though there is a katakana character ヷ, most of the time when I see
something that is transcribed into Japanese as /va/, it is in the form ヴァ
(say, for example, in the title of the anime series 革命機ヴァルヴレイヴ). Similarly,
the forms ヸ, ヹ, and ヺ seem to be fairly rare too.

I can somewhat understand the rationale for using ヴィ and ヴェ for ヸ and ヹ given
that ヰ and ヱ are almost obsolete in the contemporary written standard, but ワ
is still a very common sound.

Is there a particular reason why the two-character form seems to be preferred
over the single-character form?




I will hazard a guess here. If va was written ヷ then the entire v- line would
probably have to be written with the w- line for consistency. I think the
problem is that except for wa, the members of the w- line are strange. There
is no wu. wo is only used for one word and we, wi are not used, meaning people
are not as familiar with them.

People may have gotten annoyed by these factors and decided to use ヴ_ because
it is more convenient for representing all of the v- sounds.

