In the common guide/esper BL trope, espers are superhuman beings that possess special powers that are uses to fight monster that usually arrive through gates that start opening around the world dropping these monsters onto human civilization. Espers are sent into the gates to fight and defeat these monsters in order to protect humanity. Fighting these monsters, however takes a great toll on espers and expends a great deal of energy, which may be referred to as life force or life energy or something else, depending on the author. The solution to this is guides. Guides have energy that regenerates and an extremely high rate and are able to replenish the deleted energy to espers through physical contact. Guides and espers are ranked by letter, with S being the highest, based on the amount of energy they are able to regerate at a high rate or the powers that they have. Michael/Eve is the most powerful and an S level esper, but Adam is only a B level guide, which is why guiding can be so hard on him. This is the situation that led to the other guide stepping in, resulting in that confrontation that got them locked up in this facility now.
In some series espers and guides are born or awakened naturally and discovered by whatever organization is responsible for handling the threat of the monsters and given a rank. In this series, espers were artificially manufactured with Michael being the first and original Esper created and used as a prototype and source for creating all other espers, hence the psychic connection and him being referred to as "father".
At the start of the series, the monsters have already been eliminated and espers are no longer needed. We are introduced to Eve (formerly known as Michael) after all his memories have been erased and he is told that Adam will be his "new" guide. We then learn that Eve and Adam were paired prior to the eradication of the monsters but all of Eves memories have been erased and he is know named Michael.
We don't know anything about their relationship other than there was something that happened that led to Michael erasing some of Adams memories and they were separated and Michael was restrained.
This chapter is the beginning of Adam being reintroduced to the memories that Eve/Michael took away from the past when Eve was still fighting monsters.
I don't get it!?