I think the manga will end in three chapters.
At least that's what I would do in this situation. You don't have to agree but I would end it this way:
ch 40 - Maria defuses the bomb only to find out it was fake, the chapter ends with Okaya approaching her and calling her by her real name.
ch 41 - Okaya gives the stereotypical "I knew from the begining, so I had to outsmart you" speech to which Maria replies with something along the lines of: "You can't outsmart the justice" and stabs him with the wire cutters. Why? Because he wouldn't anticipate her killing him in front of everyone but she has nothing to lose now.
ch 42 - Maria gets arrested, confesses to killing the other four teens (yes, she covers for Yuda) and gets death sentence. Time skip. Maria's execution. Among people watching it there is her husband but also Akiji. Someone from the audience (police chief?) calls her a monster before the deed is done. After the execution, a rookie cop comes to the husband and says something along the lines: "She wasn't a monster. She saved my life. It's a debt I will definitely repay", then he looks at Akiji (yes, it's Yuda). The end.
At least that's what I would do in this situation. You don't have to agree but I would end it this way:
ch 40 - Maria defuses the bomb only to find out it was fake, the chapter ends with Okaya approaching her and calling her by her real name.
ch 41 - Okaya gives the stereotypical "I knew from the begining, so I had to outsmart you" speech to which Maria replies with something along the lines of: "You can't outsmart the justice" and stabs him with the wire cutters. Why? Because he wouldn't anticipate her killing him in front of everyone but she has nothing to lose now.
ch 42 - Maria gets arrested, confesses to killing the other four teens (yes, she covers for Yuda) and gets death sentence. Time skip. Maria's execution. Among people watching it there is her husband but also Akiji. Someone from the audience (police chief?) calls her a monster before the deed is done. After the execution, a rookie cop comes to the husband and says something along the lines: "She wasn't a monster. She saved my life. It's a debt I will definitely repay", then he looks at Akiji (yes, it's Yuda). The end.