There's a reluctance that has Rukia biting her lower lip at the first remark. She'd be a fool to believe with any level of certainty that Ichigo's life will pan out at the same rate as any other human. He's not wearing a gigai, he's not currently using any tools to normalize that in particular, and Rukia's eyes fall shut for a moment with the doubt. There's just no way for her to know. No way for anyone to know, and in this instance she can't help but think it hurts, the lack of predictability.

Because that's what birthdays are for, aren't they? Reliable means of measuring one's life.

So instead, she settles next to him, raising a playfully judgmental brow at the uneven slices of cake. Can't even manage to normalize those, Ichigo?

"I'll be ashamed of you if you can't get it gone in one. It's not a very big cake," Rukia points out, even though truth be told, if she tried to eat all of that in one swoop, it'd likely make her sick.