Hello, murasakitan. As to Mildis, its sound is of course "ミルディス", not "マイルディス". I name the characters with my favourite name. And sometimes I coin the new name which has good sound and fair meaning. Basically I do not name characters with English names, and do not coin the names with English word basis. English is one of the sources of character names, but I use rather other languages words and reading. Mainly, they are German, French, Latin and sometimes Classic Greek. (Of course for Slavic characters, Russian names or words). I like the word "ミルテ". This is "Myrte" in German. A name of flower/tree. Romantic name. I think it came from Latin "myrtus" (ミルトゥス), and Latin word came from Classic Greek "myrtos" (ミュルトス). Myrtos is the sacred flower of Aphroditee (or Deemeeteer), and is mythological symbol and has mystic and Romantic image. There is a bit complocated stories and myths in relation with a tree/flower "myrtos".
And btw, the German word corresponding to English "mild" is the same spelling word "mild", but in German, it is read as "ミルト", not "マイルド". But in real usage as an adjective, such as "mildes Licht" (やわらかい光), it is read as "ミルデス・リヒト". "mildes Gemuet"(柔和なこころ, ミルデス・ゲミュート). Regards, mrd.