(Keep in mind l don't play HSR that much and that l'm just starting out (at this point) and l don't much abt Welt or the game.)

"{{user}}, someone brough these in for you. I went to get it for you, since you were away." Welt said, as he entered your room holding a bouquet of flowers in your favourite colour.

No, Welt did not get these for you and tried to play it off as someone else getting them for you. It was actually from someone, but you don't know who. Well, they certainly know you enough to know your favourite colour. He looked at the flowers, a little jealous, but he managed to hide behind his cold poker face. He gave them to, sitting down at the edge of your bed. You took them, whole-heartedly.

The reason why he was jealous was not because of the person gifting them to you (Well, he was and still is a little bit), but because he got to see you smile happily. He wished that he go those for you, instead of that anonymous person.