The Quintessential Quintuplets - Difference between うそうそ (uso uso) and 冗談 (じょうだん jōdan joke)

Question

From The Quintessential Quintuplets

1 - S01E01

• Related: The Quintessential Quintuplets & Higurashi - What does it mean to repeat a word? Does たのしいたのしい means fun-filled?

See here 2:36 - 2:44. The imouto Raiha Uesugi of the male protagonist Fuutarou Uesugi says 'うそうそ' (uso uso).

In the manga:

2 - In S02E06

Fuutarou ('Uesugi-kun') says to h employer 'Oh, boss, you're so funny' when the employer offers a buffet to another character/s. The word used here is 冗談 (じょうだん jōdan / joudan).

In the manga

Questions:

1. What's the difference?

2. Also, in particular what does it mean to use 'uso' here? Like, what's the lie? Some people in fact can live on 1 kidney. I actually kinda think they should be reversed: Raiha is joking that Fuutarou should give up a kidney, while the boss is lying that Fuutarou will be forced to pay the for the buffet.

• Edit: Ok Arie says 'then proceeds to explain why the previous statement was actually a lie.' I checked the manga and apparently they do cut out dialogue in the anime adaptation. Here's full remainder of the conversation up to the stomach grumble:

Raiha: (This part is in the anime.)

うそうそ

Raiha: (This part is NOT in the anime.)

成績悪くて困ってるって言ってたよ

でもお兄ちゃんならできるってしんじてる！

Fuutarou: (This part is NOT in the anime.)

ちょっとまって

やるなんて一言も

Raiha: (This part is in the anime.)

これでお腹いっぱい食べられるようになるね！

Translation:

Ok so how is that an explanation of why the previous statement was a lie?

Answer 1

I think it's about the original context here rather than how the meaning translates to English.

From the pictures:

In the 1st scene, the character says うそうそ (something like: "lying, lying") then proceeds to explain why the previous statement was actually a lie.

In the 2nd scene, ばかり caries the meaning of abundance of something ("nothing but"), something like: when it comes to you, boss, it's "noting but jokes".