And...it's gone...

They had to hide the tail so maybe the tucked it in his shorts, like for his ears he was wearing a jumper to hide them. And they tried to make it look like ear muffs....... So yeah

I think his feeling heartbreak for the first time in his life made him able to turn full human only for a moment before turing back to half leopard.

I think this love deception (because he understood that Shingo and Keichi love each other) made him grown up a little and lose his innocence. So maybe this shock made him hide his ears and tails... I don't know but you were right, he clearly had no ears and tail...