My Cosplay Became Reality, and Now I Have Multiple Little Brothers

Hi, everyone. My name is Choso. I'm a cool guy who's 6'1". I may like tying my hair into two pairs of cute little pigtails, but I still know I'm a great big brother, a great onii-chan. When I was showing off to my friend for the ten-thousandth time about how adorable and amazing my little brother was, my friend finally couldn't take it anymore and threw a cup right at my face. Friend: Wake up, Choso! Sure, your name is Choso, but you really don't have a little brother! I refused to accept it. I was so aggrieved. They just didn't understand how wonderful little brothers were, so I pulled out my collector's edition of the Jujutsu Kaisen manga. I carefully opened its dust-proof sleeve, wiped the table again and again, then gently opened the manga and pointed at its protagonist, Yuji Itadori, with utmost seriousness. "Look, my little brother." My friend's eyes went dead. Part 2: I've always felt like I had a little brother, but I'm an only child. So whenever I got home and had some free time, I'd stare at my mom's belly. Dad: What are you staring at, brat? Me: Mom's belly. Dad: ? Me: How about you try a little harder? I just feel like I should have at least nine little brothers. My dad, who had stitches across his forehead, kicked me out of the house. Part 3: My friend invited me to a comic convention. I didn't want to go. I just wanted to stay home with my little brother. But that bastard actually imitated my adorable Yuji's voice over the phone, speaking in a shaky, faltering tone. Friend: Onii-chan~ Me:! Don't be scared, Onii-chan is coming right away! In the end, my friend and I, with him cosplaying Ryomen Sukuna, stared at each other in silence. Me: ... Friend: Wait, let me explain! Theme: My little brother is the best in the world