I got this request and I just loved the plot! Hope you enjoy this!
Anime: Diamond No Ace/ Ace of Diamond
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"Carlos, you have to help me!" You walked after the baseball player.
"I don't know. Get him a baseball." He said, shrugging.
"Do you know how many baseball's that boy has." You ran in front of him causing to stop walking. "Enough to make me trip at least once a day."
"Why are you even asking me?"
"Cause you're his friend. His teammate! You should know something!" 
"I don't know what to get him. Go ask Harada, he might know." Carlos walked off the the fields. You huffed and pouted.
Let me explain the situation a bit. You wanted to surprise your boyfriend, Mei, cause of how down he's been since he lost the Nationals. You were tired of seeing him lock him self in the dorm, mainly cause he locked you outside, and you wanted to cheer him up. The only problem is, you have no idea how to. You were planning on just getting him a present but you had no idea what. So you decided to ask his teammates see if they have any ideas, but you've come up empty so far. Deciding to take Carlo's advice you went to find Harada. I mean he is Mei's catcher he has to know something right?
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"I've got no idea."
"Are you kidding me?" You practically yelled.
"Sorry (Y/N), the only things I can think of he already has."
"You were thinking of a baseball weren't you?" You crossed your arms.
"Yeah." Harada scratched the back of his neck. You groned.
"I have no idea what to get him. Maybe I should just get him a baseball."
"Get who a baseball?" You wipped around to see Mei walking over to where you and Harada stood.
"Nothing! Nobody! We weren't talking about anything!" You said nervously. Mei raised an eyebrow but didn't say anything.
"Ok. Then what brings you here? Coming to watch your amazing boyfriend practice huh?" Mei asked as he wrapped an arm around your shoulders.
"Uh yeah! Of course. It's good to see you out of the dorm." You said.
"Great! Harada to the bullpen!" He ran off. You started walking after him when Harada stopped you.
"If you're going to get him something, make it special." He patted your shoulder and walked after Mei.
Make it special huh?
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"It's perfect!" You said to yourself as you put Mei's present on your desk in the dorm. Deciding you'll wrap it later, you stretched your arms and walked to the bathroom to put some pajamas on. Mei won't be back till later, as the practice will sometimes run late into the night, so you'll have plenty of time to wrap it and get it ready.You walked out the bathroom only to see his present was gone.
"Did it fall off the desk?" You asked yourself.
"So this is the baseball you were talking about."
You wipped around to see Mei holding the baseball you got him.
"What do you mean?" You asked.
"I heard your conversation with Harada. I only pretended not to know to see if you would admit it. But alas, you didn't." He said tossing the ball up and catching it. You took the ball from him.
"Because it was supposed to be a surprise." You pouted.
"Well it's not a surprise anymore." He said falling onto the bed.
"Why'd you get a baseball anyway? Do you know how many I have?" He asked and pointed towards a small pile of baseball's in the corner of the room.
"Cause it's not a normal baseball." You said laying on the bed next to him.
"Why? Does it have magical powers?" He teased.
"No! Look." You showed him the other side of the ball that he didn't look at. Written on the side was the date that you two had began dating and both of your initials below it.
"You...You did this?" He asked softly.
"Yeah. I'm not sure if you could use it cause it has something one it but-" Mei cut you off by pulling you into a kiss.
"It's perfect (Y/N). Don't worry about it." He said making you blush.
"Thank you. I love it." He said.
"You're welcome. Now let's go to sleep." After putting the ball up and curling up together in bed you were almost asleep when Mei broke the silence.
"You still got me a baseball though. It's another one you could trip over!" He laughed.
"You better not leave it on the floor, or so help me Mei."
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I hope this is close to what you wanted...