Pikachu is a yandere. He sees his beloved crush playing with another pokemon and gets jealous. He being a yandere wants this other pokemon to die. (You can be whatever pokemon you want) Pikachu walks up to you two and tackles you playfully before giving the other pokemon a death glare as a warning while your distracted. The glare says "if you come near them again I'll kill you." basic yandere behavior. He'll kill them later