Toaru Majutsu no Index: New Testament - Volume 15, Chapter 2: Peace, or a Trap Laid — Board_Game.

[Ding, your frog was afraid of your death, so he went on a trip overnight and stole a shelter for you! 】

…

Reborn into a world of global catastrophe apocalypse.

In the face of global recovery, zombies, fog, meteorites, prehistoric creatures, glaciers, earthquakes, acid rain and other devastating global disasters, the only thing Ye Su has to do is to survive.

Unexpectedly, he got a traveling frog when he arrived. The frog was afraid of Ye Su’s death, so he simply stole a shelter!

Ye Su: “???”

But what’s even more outrageous is yet to come.

[Ding, your frog is afraid that you are not stable enough, so he stole the source of fire for you]

[Ding, your frog was afraid that you would be bitten, so he stole the antiviral potion overnight! 】

[Ding, your frog stole the Zanpakutō for you! Additional Asura – Blade Skill! 】

So, when everyone was avoiding zombies, disasters, despairing for food and water, Ye Su had already carried a big knife, drove a car, and came out for food!

- Description from novelbuddy

Arakawa Kouki is reincarnated to a Japan with a different history than the Japan he knows with the memories of his previous life still intact. Kouki was discouraged, “Aren’t reincarnation stories supposed to be at some fantasy world filled with swords, magic and elves?!”

The servant looked at the grieving princess. “Your Highness, the Regent Prince sent your scholar fiancé to the Western Butcher’s daughter!” 

The princess gritted her teeth, speaking to her servant that it matters not as she has other suitors in line. Many days later, much to her dismay, the servant ran in a hurry. “Your Highness, the Regent Prince expressed his intention of becoming your suitor! All other men in line were sold to Gou Lan Red District!”

The princess was distressed. She said to her servant it matters not. She’ll soon be married to Prince Fuma. Then the uneventful came. The servant once more ran to her, almost tripping in the process. “Your Highness, Prince Fuma was imprisoned at home! Meanwhile, there’s a red sedan chair waiting at your residence for your marriage! It was led by the Regent Prince!

The princess was stunned. For a day such as this to come, it seemed impossible. This nothing but a sad story of a female boss crossing back in time to hold the thick thighs of the big boss. But while raising him, she was eaten in the process.

- Description from Novelupdates

The MC entered the body of the An family eldest son, An Ziran, an arrogant 16 years old boy who weighed 78 kg (~171-172 lbs), who only knew how to eat, play and sleep. Seeing his current body, An Ziran decided his first priority was to LOSE WEIGHT!