The Characters of Orbius, Jinn-Lir, Wonn-Lir, and Coin are going to be used for Narration and Exposition of the Cartoon, just like Shiro is both a Character and a Narrator of the Log Horizon Anime.

Wonn-Lir is the Narrator for parts of the story that are Dark as an Anti-Hero Narrator Type. Jinn-Lir, his brother, covers Narration for the Hero Narrator Type. Orbius Narrates the more Ominous and Ancient Topics, and Coin Narrates for Specific Worldbulding.

So, you have 1 Old Narrator, 2 Middle-Aged Narrators, and 1 Young Narrator. These voice actors/actresses must be of the proper age as alligned with their character. An Old Man does not get to play Coin, and a Young Woman does not get to play Orbius. Jinn-Lir and Wonn-Lir should be played by dudes in their 40's.