He killed himself in the first dimension by tearing out his own heart to then wake up in the second.

 He was deeply confused and couldn't remember specific details of the past until I burst into his room annoyed and scolded him, "Hey, are you coming out now, or do I have to kick your ass?"

 His eyes widened at my sight, and he trembled, every trace of color draining from his face. He looked so scared and anxious.

 I stared at him dumbfounded, "Uh, Gojo, what's up?" 

He took a cautious step toward me, arms half outstretched, "M-Miura?"

 I looked at him dumbfounded, "Huh?"

 He took another step and another. I took a step back slowly out of fear. He reached for my arm and pulled me into his arms tightly. I was startled, and his rapid heartbeat echoed in my ears. He hugged me tightly, burying his face in my hair at my neck.

 I was so confused, "Gojo, you're scaring me." 

Suddenly, he sobbed so loudly that it startled me again, and I tapped him on the back, "Is everything okay?" 

He sobbed again, his tears wetting my uniform, and joyfully exclaimed, "Miura, you're alive!" 

I lightly slapped his shoulder, "Dumbass, what else would I be? Are you high or something?" 

He breathed heavily, actually inhaling my scent, which made him look like a creep. He let go of the hug and cupped my face in his hands. His eyes were red from crying, the first time I'd ever seen him like that.

 I looked at him wide-eyed, "Are you sure everything's okay?" 

He looked at me happier and gave me a kiss on the forehead, not moving. 

His lips were still on my forehead, and he whispered my name softly, "Miura... Miura, please never leave me again." 

I took his hand in mine, looking at him questioningly, "What are you babbling about?" 

He released his lips from mine and stared deeply into my eyes, "Your eyes must stay alive."

 I kicked him in the shin, making him flinch in pain and laugh, and the remaining tears rolled down his cheeks.

 I crossed my arms over my chest, "I don't know what's going on with you, but get yourself  together."

 He cleared his throat and straightened up, "Right..." 

His gaze briefly followed to the mirror, and his eyes widened, "Miura, how old are we?" 

I looked at him completely dumbfounded, "HUH? Are you stupid?" 

He didn't answer. 

I hesitated, "We're... 18. Why?" 

He took a deep breath and smiled, then put an arm around me, and we walked out of his room together. I was completely confused but ignored it for the moment. We went outside where Toji and Geto were waiting for us. 

He stopped dead in his tracks, his mouth hanging open, his body tensing, which I could feel. He went into a slight fighting stance. I looked at him confusedly. Toji and Geto laughed and looked in our direction. 

Toji raised an eyebrow, "Well, well, you finally decided to come out, you little brat." 

Geto sighed happily, "We had to send Miura to get you."

 I laughed, but Gojo was frozen, murmuring softly to himself, "Suguru...Toji?" 

Toji scratched his head annoyed, "Now hurry up, we have a mission!"

 I pulled him by the arm, and he hesitated as if he couldn't believe his eyes, "Y-yeah, sure...!" 

We went to Urahara, who gave us the mission to protect Riko Amanai, the star plasma hull, until the day she merges with Tengen. 

He stared at her photo the whole time, muttering to himself like a madman, "Amanai..." 

I tapped him concerned, "Hey... everything okay for real?"

 He hesitated but then smiled and ruffled my hair, "Yeah, everything's fine as long as you're safe."

 I got butterflies in my stomach, blushed slightly, and turned away immediately.

We also met Riko. Gojo devised the whole plan for us to take her directly to the Jujutsu Academy. I was amazed at how well thought out his plan was. He set up new barriers, increased security, directly admitted Riko to the Jujutsu Academy, and what surprised me most, he didn't assign me any tasks. 

Two weeks had passed now. I was with her in the lake area, among the cherry blossom trees. We walked along there, my hands behind my back, taking in the peaceful sight. 

"So, Riko? What's your decision?"

 She looked down at the ground as she walked beside me and chuckled lightly, "I don't want to be selfish... I was born to serve as the star plasma hull, but now, in these two weeks, something became clear to me..." 

She looked at me determinedly, tears in her eyes as she took my hand excitedly, "Miura, I want to live!" 

I looked surprised and happy, wanting to hug her when suddenly her head fell to the ground. I froze in horror, looking at her. I felt sick to my stomach, terrified, as her body fell beside me without a head. I screamed in shock as her blood covered me.

 Suddenly, the area around me turned into a dark place. A hooded man appeared in front of me and pierced my heart with his hand, pulling it out. Blood surged up, and the area returned to normal. The last thing I saw was Gojo on his knees, looking at me in horror. His lips trembled, his mouth hanging open. 

It was the moment when I remembered the first dimension. I spat blood one last time before falling to my knees and then dead to the ground. 

Gojo stood up like a lifeless corpse, and before Nicol could teleport away, he blew her up into the air and then strangled Sasori with hatred. He teleported in front of me, bloodstained.

 He looked up at the sky, weeping, "Forgive me..." 

His gaze returned to my corpse, and he reached out, stabbing his own heart. More blood fell on the ground, adding to the pool already there from Riko, me, and now Gojo. 

Geto and Toji screamed in shock, "GOJO!" 

The surroundings froze, and he fell dead beside me.