Until then, Tokyo/Japan was considered as a highly secure city/country [you used Tokyo as a reference, so you must say "city," since it's a city and not a country; or change Tokyo to Japan], however but this terrorism attack caused many to consider question about their country's security to raise caution for defense against domestic terrorism and strength security for the domestic terrorism attack [it seems like you tried to give a lot information here, but simple is good most times]. this The following summative summary will, in order to figure out what extent did how much the Tokyo gas attack of 1995 influenced Japan’s approach to security, identifies and compares its security structures before and after the gas attack with the emphasis on understanding of Japanese's cultural and socio-psychological features. An Analysis of the Tokyo gas attack reveals the issue in Japan’s security: a lack of security enforcement to against terroristic attacks, very collective mindset as cultural code, a strong band of hierarchy by social positions.

Corrections Part 1

More than 5,000 people were injured and 12 people were had killed by in the Tokyo underground sarin gas attack in 1995 (Watt, 569). This very  was the first biochemical terroristic attack that happened to occur in Tokyo, the capital city of Japan, which shocked all over the world and illuminated highlighted ["illuminated" doesn't work so well in this case] the terror that of an indiscriminate alternative biochemical attack can cause terrorist attack [I wouldn't use the same term twice in one sentence].