Correct grammar and spelling errors, and add necessary punctuation.
When Akihiro was 7 years old he decided to go swimming in a lake with his father, Akihiro told his father that he could not hold his breath for too long under water and that scared him, his father explained him that the fear he felt made his heart go faster causing the oxygen in his body be consumed faster, and if he wanted to maintain his strength he needed to stay focused, calm but consistent.
When Akihiro was 7 years old, he decided to go swimming in a lake with his father. Akihiro told his father that he could not hold his breath for too long underwater, and that scared him. His father explained to him that the fear he felt made his heart beat faster, causing the oxygen in his body to be consumed faster. He also told him that if he wanted to maintain his strength, he needed to stay focused, calm, but consistent.
The same with this if there needs to be.
The user remains in a state of extreme relaxation and realizes several fast-as-flash slices.