Step 1: The question describes unwanted, persistent, obsessive attention directed by one person (or group) toward another individual.
Step 2: This pattern of behaviour is termed stalking. It is characterised by harassment and intimidation and may include physically following the victim or otherwise monitoring them.
Step 3: The term stalking is used in psychology and psychiatry and is also defined as a criminal offence in many legal jurisdictions.
Step 4: Perceiving, following, and pressurizing each describe only an isolated act and do not capture the obsessive, repeated, attention-seeking pattern; stalking is the correct term.