I think the last chapter was to explain than in the next chapter her brother is gonna be heartbroken since he's been dumped which means it's the first time he's loved someone so much to care
Which is to indicate senpai truly lives him but he doesn't know how to show it and instead he hurt Itou because of his jealousy
And since the sister will notice the change in her brother's behavior on the break up, she'll tell Itou and he'll go to senpai
Well, that's all my guess, we'll see in the next chapter ╮(￣▽￣)╭
I think the last chapter was to explain than in the next chapter her brother is gonna be heartbroken since he's been dumped which means it's the first time he's loved someone so much to care
Which is to indicate senpai truly lives him but he doesn't know how to show it and instead he hurt Itou because of his jealousy
And since the sister will notice the change in her brother's behavior on the break up, she'll tell Itou and he'll go to senpai
Well, that's all my guess, we'll see in the next chapter ╮(￣▽￣)╭