He didn't bother to correct her on the Master thing. He tried several times, but eventually, he seldom corrects her because he's used to it...and admittedly, he learned he liked it. She's adorable and she often lights up calling him that, and over time, it was a form of endearment.

Seiya's usual thoughts wind down in the evening, especially after a busy, hectic day. He has plans to make dinner, then showers, and then wondered what he should do for their usual routine playtime before he goes to bed. Following her voice, he sensed she is the garden, only to stop at the door of the living room and found a collection of stuff...for...what looks like a nest? His thoughts and plans became derailed.

"Wah? Wait, what is this???" Leanne got some 'splaining to do! "Leanne! What did you do to the living room?"

He can't recall why a mischevious heron might want to build a nest. He read the pet-keeper's guidebook once, and then forgotten about it since he had little time to read. For now, he figured Leanne perhaps gotten a little creative and maybe wanted to do something artistic while he's away, but didn't mentally connect it to a mating behavior.