ep 20. Eru and Hotaro go on a date because this is what this show is now.
They framed their date like an actual date, with Hotaro standing in the cold, waiting for his girlfriend, and he visibly lights up when he sees her. For her part, Eru was quite confident and expectant as she first greeted Hotaro, and looked quite pleased when she saw how stunned he was by her appearance. I wish more anime romances were like this, or at least would get to this point where the main pair are this comfortable with each other.
The rest of the ep puts Hotaro in a visibly uncomfortable setting. Eru clearly doesn't act like she's superior to him, she just doesn't know how to express her respect for him in a way that he could accept, so her being perfectly comfortable in that world only put him further off-balance. This show (at least this ep) goes full-on "my girlfriend is secretly a princess" fairy tail mode. I said it last ep, but I really did not expect this show to have class disparity as an obstacle for its main pair, but it's pulling it off pretty well.
The shed bit had me worried. Not only could I not see anything for most of it, this cliché forces characters to get closer in a way that feels contrived, but Eru bringing up her status pushed them back apart and that partly salvaged the situation. Eru offering her kimono's obi string (without even knowing what Hotaro's full plan was) was a bold act of literal and figurative undressing for Hotaro,
a demonstration of her complete faith in him.
Of course, Hotaro doesn't really get this because anime boys never do, but I am willing give him a pass. He was having a bad day. Even after a season and a half of solving mysteries and making Eru happy, he still feels like a burden to her, much like Satoshi doesn't feel like he's good enough for Mayaka. Eru is clearly committed to this relationship with Hotaro, but given his insecurity, she has a difficult road ahead of her.