Simplify the following text for a Grade 11 native English-speaking person.
Original: Sakoku ( Japanese : é -- å 1\/2 , literally `` country in chains '' or `` lock up of country '' ) was the foreign relations policy of Japan under which no foreigner or Japanese could enter or leave the country on penalty of death .
Simplified: Sakoku was the foreign relations policy of Japan under which no foreigner could enter nor could any Japanese leave the country on penalty of death .