Even though cheese forest seems like a simple game there is a lot of lore, from what is in the game now the fallowing lore is cannon. There are a total of 6 characters; the player, the park ranger, the cave man (or "???" as he's called in the game), Ethan, Alex and Carlos (the boss). The park ranger and Ethan only show up 1 time each, there isn't any known lore behind the park ranger however for Ethan it is known that he also went into the other dimension to try and stop the radio from seeping into the main dimension with the radio active cheese to  the bomb but was not successful. The 1 and only note written by Ethan is found in the bunker where there is cheese and many batteries, there is no cannon reason for the objects being in the bunker.  Carlos is the boss and your (the player's) job is to investigate the cave, the boss has also placed a flash light in the watch tower. Alex is another person who has explored the forest and found strange things gowning on, like red creatures or a suspicious amount of radiation around the watch tower, however there is nothing saying if they went through the portal or not. The cave man or known as ??? in the game, is the person who was placing cheese around the forest, the creator of the portal and the one who tells you you need to stop the nuke. there is no sign if he went through the portal or not. The red creatures are something that is mentioned by Alex in the shed building however it is said there are only 2 but there are actively 3 where the 3rd one is in the watch tower and harder to see. The rat creatures in world 2 are there because they feed on radiation, there are many of them, it is said by the cave man that they walk on 2 feet and are 4 meters tall. 

On the speculation side of things, or things that are not cannon but have backing up evidence that could prove these theories true towards the lore of Cheese Forest. There is no official lore saying who the came man relay is but the biggest theory is that the cave man made the nuke, he was the only one to know about it and without him having made that portal in the frost in the first place there is no way he could have known. But who is the cave man? Alex knew there was radiation but had not done anything about it it is possible that the cave man is a un-mentioned friend of Alex or just Alex him self. There is also speculation that Ethan is the cave man because he was the only other known person to have enters the portal. For Carlos and the park ranger there isn't much information, they could both equally be the cave man because there are slight possibility but there is no sporting proof.