Lupin and Clarisse meet for the second time in the castle's secluded tower. What follows will surely melt your heart, whether you have a heart or not. To put into detail, Lupin offers Clarisse to "steal her away from Cagliostro", but she refuses, thinking he's no match for Cagliostro and he will surely be killed. Hearing this, he laments on, if only she'd believe, he could fly through the air or drink up every single drop of water from the largest lake in one gulp. Finally, in order to give her a reason to have faith, Lupin (almost magically) produces a tiny rose from his hand with a string of tiny European flags attached to it and gives it to Clarisse as a keepsake.
Even more heartwarming in hindsight is the fact that Lupin accomplishes everything he says he could do. He flies through the air to rescue Clarisse, and drains the lake in the course of his ultimate showdown with the count.
At the end, when Zenigata catches up to Clarisse just after Lupin's departure.
Zenigata: Blast it! I was one step behind him. Lupin stole something again! Clarisse:No, he didn't steal anything. All he did was fight for me. Zenigata: (looking straight at Clarisse) No, he stole something quite precious... your heart. Clarisse: (gasps, then smiles while nodding) Yes. Zenigata: (steps back, saluting her) Well, if you'll excuse me. (winks, resumes Stern Chase)
Clarisse asking Jigen and Goemon, two random strangers that she knew only as friends of Lupin, to come back alive during the climax. It warms both of them in that she called Jigen "sir" and Goemon admitted that she's lovely (doubling as a funny moment). Furthermore, Jigen proceeds to wear the wedding crown she left behind on top of his fedora for the rest of the movie. Including a major shootout with the Count's men.
The sight of the entire Tokyo police force waving goodbye to Clarisse.
Lupin admiring the lost underwater city. "This is a treasure meant to be shared by mankind. Too big for my pocket anyway."