The code is identical to the English version except for what you name her. Because the vast majority of those visiting this site cannot understand Japanese (myself included) the steps have been outlined one by one so that the code is done correctly.
Step 1. Recruit a female character and give her any element.
Step 2. Use the 2nd name choice (katakana) and insert the name using the exact 3 signs below.
Step 3. Make sure that your character is chaotic or neutral. If not, then cancel the recruit and try to recruit again (you only have to insert the name once).
Step 4. Take the character into a battle and persuade a male enemy (I suggest a soldier).
Step 5. After acquiring the charm emblem, change the character to a witch (note: the character still needs to reach the stat requirements).
Deneb can use witch and summon magic with the additions of Faith, Tranquillize, and Cursed Existence. Her charm ability is excellent. Get her at the lowest level you can to take advantage of her high stat growth.