In the apartment where he lives and teaches the three neighbor girls about what they are, there is a small kitchen.
There's hardly any counter space to do half of the things he instructs them on, and only one of them could work with him in it at a time. Umi, the more vocal of the three, always complains about not having enough room to work, and doesn't he know how hard it is to get into the fridge for a snack when he's putting away dishes?
Clef always sends her back to her incantations when she gets particularly…obtuse. Despite her initial complaining, she does have the clearest diction when it comes to her incantations of the three of them because of that practice.
Hikaru never bothered complaining about the size, always grinning and saying, "We'll make it work."
He always ruffles her hair at that, smiling at her. But her eyes would aways wonder to the stove. Specifically, to the kettle sitting on the stovetop. He knew that all three of the girls had their questions about him and about how he knows what he knows–but he knows that most of those questions get focused on that kettle.
Finally, one day, after they'd worked very hard, he sat them at his small table and brought out the kettle. He could see the spark in their eyes immediately–they were many things at this young age, but they were not yet subtle.
He set it gravely on the table in front of them and said, "This. Is a very important tea kettle."
They kept their eyes glued to the kettle, listening intently.
"It's a magic kettle."
He saw them tense for a moment, quickly sneaking glancing at each other before looking back at Clef and the kettle.
He tapped the top of it, "This was a kettle that my mother gave to me when I made my first potion. She looked at me and said, 'Listen, my Sky, what we do and what we are, takes a lot of energy. And tea is good to help your soul. Use this to help come back.'"
He leveled his gaze at the girls, hardly containing his smile at them, "Now you three have come a long way since your first potions, so I think you're owed a cup of tea from my magic kettle."
The girls took a collective breath and looked at each other again, all grinning at each other.
Very quietly, Fuu asked, "Are you sure?"
He smiled at her, "Of course. My mother would have loved you three."
All three of them smiled at that as Clef went to make them tea. He knew they would remember this, and he was glad that he'd given them something real about himself for them to know.
He was their teacher after all.