would I be missing the meaning "beautiful ocean"/"beautiful sea" of ミ{mi}ミ{mi} if I used only katakana?
Yes. Whether you use hiragana (みみ), katakana (ミミ) or romaji (Mimi), no one would think you're referring to the ocean. If anything, people would imagine this word, which is not what you want to convey.
If you heard that Mimi meant "beautiful ocean" from someone, I think that person had the kanji 美海 in mind, which is one of the many combinations of kanji that can be assigned to the name "Mimi". 美海 indeed carries the meaning of "beautiful (=美) ocean (=海)". I would like you to read this Wikipedia article about the Japanese writing system, but the kanji 美海 is mandatory to convey the meaning of "beautiful ocean". If you write it in hiragana, katakana, or romaji, the intended meaning won't be conveyed.
Also note that 美海 is a girl's name, not an ordinary word defined in regular dictionaries. It doesn't make much sense outside person names. If you used the kanji 美海 in your logo, people would wonder if it's an anime character goods or something. What's worse, "Mimi (みみ)" is not the only reading of the kanji 美海; it can be read also as みう, みうみ or in other rare ways. A common workaround is to include both kanji and kana/romaji in your logo, as shown here and here.
I read all the articles you sent me, it helped a lot to understand a little more, as I am a newbie, I still have a lot to learn.
One last question, I don't want to get in your way.
In this case, my logo is something like: "Mimi's Ikayaki", I want to imply that the restaurant sells Ikayaki dishes and has an owner called “Mimi”.
To convey this meaning that I want to give, how would the writing in kanji look like?
Are any of these correct for this purpose?
1: イカ焼きの美海
2: イカ焼き美海
3: イカ焼き 美海
4: 美海のイカ焼き
5: 美海のイカ焼き屋
Thank you so far.
– Tsuki Aug 24 '23 at 08:18I chose the 4th option: So the logo will be: 美海のイカ焼き - Mimi's Ikayaki
Thanks, Naruto!
– Tsuki Aug 25 '23 at 00:55