Kasumi has been hooked on dating sites for some time. Because of her fear of being dumped, she can't be active in love affairs, and she seems to have dated multiple men broadly and shallowly. The reason why she continues to use her dating site even after she got married is because she thought that she would be okay even if her husband betrayed her, so she had a rather distorted view of love. And she seems to have found out that her husband is cheating on her, so she may be feeling quite lonely.
