Insane but mine (Shigaraki Tomura X Semi Yandere Reader)

Prologue

The serene atmosphere lightly lingers. The light and cool breeze brushed their skins as they stood by the field of colourful flowers. The silent environment was welcomed with open arms.

You always wished that every night was like this. No heroes, no villains. Just you and Tenko, just enjoying the views the world will offer.

Both blood stained palms held each other, the other one held their pinky up.

Both kids faced each other, the luminescent glow of the moon provided them light. The blood on their faces were visible as they stood by the grassy meadows.

They tightened their grip around each others grasp, as they stared at each other. Fiery passion burned in their eyes as they stared deeply in one another's eyes.  Such innocence, such youth... Ruined. They stood without a care in the world, for all they have were their bond. 

"Repeat after me," said Y/N to Tenko, eyes intently focused in his crimson orbs.

He nods as a response.

"I promise to be your ever loving spouse. I will be the light in your darkness, the wine in your cup, your comfort in your woes, the colour of your world. Never will I have my eyes on other people, but only to you. I promise an eternal life with you, through thick and thin, through grieve and happiness, through sickness and in health, through life and death, we will never part." You solemnly recited.

He recites back. And when he finished, he grins at you.

"This is like the wedding vows that Nana told me," he shyly reminisces, as his bloody palms grew clammy. He still kept his pinkies up to avoid withering his 'spouse' into cinders.

"Except this is better!" You chimed at the smaller boy. "Newlyweds divorce and leave each other! And we will not do that, right?"

"Right." The boy agreed. "Where did you get these things anyways?"

"Hmm? The vows?" You asked. "Oh! You know those books in Master's shelves?"

"The one you're not supposed to touch?"

"Exactly! I gained access to it and I read it in secret!" You responded.

Both children went through a child shouldn't. Whether it's an accidental murder or purposeful murder, both killed those who raised them when their quirks manifested.

A two sides of a coin. Always having each others back no matter what happens.

Both children that will face every consequences and trials in life, together.

No matter what happens.

Shimura Tenko.

Or maybe you know him by the name of Shigaraki Tomura.

Or maybe you don't know him at all. But that doesn't matter.

The first time Master All For One got home with that boy, you instantly knew he's yours.

Even for a five year old, you were already lovesick. An innocent lovesick who will protect your future husband from any harm! Who will comfort your husband if he ever feels upset!

You gave every ounce of your humanity for him. He truly deserves the best. You gave every ounce of your love and joy, and shared that to him! The sweet little thing was overwhelmed, he casted you away some times!

But that's just normal for couples, he'll be back of course! And if he didn't come back... Well... Let's say a few blood will be shed.

Like a loyal little cat to their master, leaving mice on the bed of their master to show their appreciation and loyalty.