This is an image of Mayuka. I tried to base her childhood hair off of the same Mayuka from 'Daughter of Darkness'.

So far my idea of her is that she takes a lot after Tenchi in that she is a hard working and earnest girl. She does look bitter like the black coffee she drinks, but she is actually a sweetheart that became a member of the Galaxy Police to protect her family from whatever crosses her path. She might have some connection with one of Seina's sons, but I can't be too sure on it. My idea so far is that her adult form is on a mission to battle some goons. Her child-self was more of the curious type, often wondering what Sasami and Amitav were up to. She addresses Amitav as 'Uncle' for the same reason Sasami addresses Funaho as 'Auntie'; She is aware that Tenchi is her biological father. She can sometimes be seen arguing with the eldest of her half-siblings as an adult, but as a toddler she was eager to help Sasami raise him and was excited for when he was born.