Minor language warning.
'.' - speaking in their minds
"." - speaking out loud
It was a wonder that Yugi was able to keep his secret for as long as he did. It was tricky at first when he really had no idea how the puzzle he wore around his neck worked. At first, he didn't really think there was anybody inside of his puzzle. He had no idea what was going on the majority of the time. At first, when he started dueling, there was something guiding him on how to win. The voice died down a bit when he was doing casual duels in school, but during Duelist Kingdom is when he really found out the truth of Yami. It shocked him, to say the least, but he also wasn't all that surprised. He thought he was going crazy for a while, but it really did feel like there was somebody inside of him who shouldn't have been.
Since he hadn't known about the spirit inside the puzzle, he never openly made a connection between them. The spirit, in turn, didn't come out of the puzzle or see into Yugi's mind unless there was an issue going on that he could sense. Anything that went on in Yugi's personal life was usually private. The moment Yugi stepped inside his home, Yami would hide away in the puzzle without coming out because whatever was going on with Yugi in his home was none of his business seeing as the two never fully communicated.
Once Yugi realized that there was somebody else in his head that wasn't himself, he knew he was going to have a rough time hiding his secret. During the tournament, he worked on being able to cut off the connection between the two. The match with Pegasus made him realize how simple it really was and he found his solution: whenever he needed to, he could just separate their minds so Yami would never find out. He knew Yami would ask him once why but then not ask again when he realized it was something Yugi didn't want to talk about it. That's just the way the spirit was; he wouldn't press the issue.
Yugi was dreading returning home from Duelist Kingdom for multiple reasons. The spirit could sense this but he didn't understand why. First off, he was worried that Yami would discover his secret now that they were friends. Secondly, he wasn't particularly looking forward to what he was returning home to. He was excited to see his grandpa, but he knew he couldn't stick with his grandpa the entire time. His grandpa shared a home with Yugi and his parents but they were in two separate portions. His grandpa lived above the game shop while Yugi and his parents essentially lived next door but connected to the game shop. It was a nice set up so that his grandpa lived on his own but he was there whenever he wanted to be there. That didn't mean he would be there whenever, though, and that was the issue.
The secret Yugi was keeping from everybody, his grandpa and Yami included, was the fact that his parents weren't very kind people. It started when Yugi young, maybe eight or nine, and it was never physical at first. His parents started fighting, usually when they thought he couldn't hear. Then they were fighting louder and more often, and then the two got physical. Shortly after that, they started yelling at Yugi and, eventually, got physical with him, too, and they never stopped. Home life for Yugi was rarely ever good. There were occasional moments where the three of them were able to sit down and have dinner together in either silence or very slight, casual conversations. Grandpa would bring the life out of his mother whenever he was over which Yugi really loved, but gramps never liked his dad so he didn't visit too often. Life was rough.
The evening he got back from the tournament, he went straight to the hospital to see gramps. Gramps practically raised him, it felt like, and having him in the hospital caused him so much pain. He sat with him until visiting hours were over and Yugi had to go home. As much as he hated the feeling, he missed his parents, too. He hadn't seen them in a while. He was scared to return home, though, because he didn't really give much reason for leaving except for 'I have to help gramps.' That obviously didn't sit well with his parents but he didn't stick around for their reactions. He couldn't, or didn't want to, witness their reactions.
As he neared his home, he felt his anxiety levels increase. Yami sensed it, as well. 'Is something the matter, Yugi? You feel oddly worried,' he commented, worried for his young friend and 'host body' so to speak.
'Just nervous to see my parents, is all,' Yugi replied, trying to keep an upbeat tone in his voice. 'I didn't give them much reason for leaving to the tournament. Hope they're not too angry.'
'I have yet to meet your parents,' Yami said, his voice sounding deep in thought. 'I've met your grandfather, even if us two haven't been formally introduced just yet, but I've not met your parents.'
Yugi hesitated for a moment. He didn't want to be too obvious that there was an issue with his parents but he didn't want to give Yami the false impression that he would be introduced to them. He assumed Yami didn't want to be formally introduced because if he told his parents there was a spirit inside of him, well, he'd be labeled as crazy and the spirit had to understand that. Even though there wasn't going to be a formal introduction, he would probably be expected to let Yami see a normal family interaction. He took a moment to form a response before saying, 'Maybe it'll be best for you not to meet them just yet. They're a bit different than the rest of us.'
Yami could sense that Yugi didn't want to talk about his parents. He could feel the worry coming off of him in waves and his thoughts seemed a bit all over the place as if he was trying to hide something but didn't want him to find out what. He decided to drop it; if Yugi wanted his secrets, he was entitled to have them. After all, it was his body, his parents, his life. Yami couldn't complain or judge, so the best thing he could do was let it go and pretend he wasn't insanely curious as to what the secret was. 'If that is what you wish,' he relented.
True to his word, Yami went into his spirit room when Yugi entered the game shop. He kept their minds separate; secret. He couldn't see into Yugi's mind, but he was able to feel the essence of emotion. What he felt was not promising. Yugi was afraid, nearly as afraid as he was when they traveled to the Shadow Realm against Pegasus. Instinct told him to take over and protect Yugi at all costs, but he resisted the urge. Yugi didn't want him to meet his parents so he was going to keep his promise.
Yugi, for his part, was not handling his parents as well as he should have. He called out for his mom when he walked inside and thirty seconds later both his mom and his dad were on him, screaming horrible things at him before his mother stormed out, cursing about her "ungrateful, bastard child" who was "such a pain in my ass." Once his mother was gone, things got physical. Without warning, his father grabbed Yugi by his hair and tossed him effortlessly against the wall. Fists were thrown out left and right and then kicks were added to the mix. Screams of how he wasn't wanted filled the air.
After a short while, his father seemed to grow bored because he, too, stormed out of the house, slamming the door shut behind him. Painfully, Yugi stood up and limped to his room. He couldn't tell what exactly kept him from crying out. Pride, maybe? Refusal to acknowledge his parents' betrayal? He didn't know, but he knew he kept his mouth shut. Once in the safety of his room, he took a moment to assess the injuries. His wrist was sore, probably from the way he hit the wall. He bent his wrist back and forth and concluded it wasn't broken or anything but would likely be sore for a bit. He shoulder ached and he could picture the foot coming in contact with that exact spot. Again, no serious damage. His stomach hurt pretty bad, though, and he was almost certain he strained some muscle in his back.
Before letting the spirit back into their shared mind, Yugi hurried to take a shower. There were some spots of blood but he couldn't tell where the blood was coming from. The stinging sensation from the shower definitely helped him with that discovery and he was able to clean each wound. Thankfully, the wounds weren't deep or dangerous so he didn't need to wrap anything. Once comfortable in his bed with his pajamas on, he unlocked his spirit room as an invitation for Yami to return.
Yami sensed Yugi's presence so he felt it was safe to come out. He opened his spirit room and exited into the real world to appear with Yugi. Immediately, he noticed the fact that there was an issue, even if he sensed it before. He couldn't make any guess as to what the issue was and he didn't want to bring it up again, so he kept it quiet. When Yugi was ready to talk about it, he would listen. Until then, he'd pretend as if he didn't think there was an issue even though Yugi could tell Yami knew there was an issue.