I will be really grateful if you identify this manga:

1. The setting is in an High School which is about to get closed forever, the main character is a male.

2. But a labyrinth/Tower appears in the school grounds. The school is then occupied by millitary.

3. The heroines were:

a.
The tsundere childhood friend and cousin of the main character: She later dies in the manga.

b. A Yamato Nadeshiko Kuudere Girl: She's the love interest of the mc. Age same as the mc but she has a Captain Rank in the Army. She belongs to some Himawari

Organization. Her Grandpa was a big shot in the army, but had disapeared in a previous labyrinth. She wants to find what he wanted to find.
Cold to the mc in the beginning. Calling herself as a tool, she later falls in love with the mc.

c. A tomboyish girl, belongs to army, and has a mechanical arm

d. A loli who also belongs to the army.

4. The main character, his best friend and the tsundere childhood friend also join in with the army to search inside the labyrinth

5. The main characters gets the fighting moves of an elite soldier (who is now a miko) implanted inside his brain.

6. There are monsters in the labyrinth.

7. The tsundere childhood friend gets killed later.

8. The MC full of remorse goes deeper into the labyrinth.

9. He later gets accompanied by a dark skinned little girl, dressed in arab clothes. The girl was raised as an Assasin.

10. He goes through different gates in the labyrinth. One gate leads him to an alternative world leading to an Arab City.

11. Another door leads him to the future, where he finds that he is engaged to the Yamato Nadeshiko girl.

Please help me find this manga. I lost it. Tried many combos of tags later, but couldnt find it.

Classmate to Meikyuu no Futekisetsu na Kouryakuhou?