Mom's gushing when she cums can be a complex combination of physical and emotional factors. Physical arousal, hormonal changes, and the depth of the sexual experience might all play a role. However, it's a very private matter and can vary greatly from person to person.
The son could cums in (come into) his mom's garden where she is tending to her plants. He surprises her with a handmade flower pot he made in art class. His mom is overjoyed, and they spend time together planting a new flower in the pot, talking about nature and how much they love their little garden.
Maybe the son cums in (enters) his mom's study where she is working on a family history project. He then helps her out by providing some details he remembered from his grandparents, and they bond over family memories and the importance of preserving family heritage.
Rather than seeking such stories, it's better to explore stories about respect, communication and healthy relationships in general. There are countless great books and movies that deal with positive relationship themes.
I'm not sure if there is a specific 'Cums Inside Kushina' fanfic. Fanfics cover a wide range of themes and stories, but this might be a rather inappropriate or hard - to - find one. It also depends on the specific fanfic platforms and their content policies.
Writing or seeking such inappropriate fanfics is unethical and violates the general moral and ethical standards of the Naruto fandom. Most official platforms would not allow this kind of content. So, I don't think there should be any legitimate availability of such a fanfic.
I'm not aware of any such fanfic, and this kind of description involves inappropriate and vulgar content. Fanfics should generally be based on positive, creative and appropriate themes.
Stories about truckers having positive interactions with families could be a good alternative. For example, stories of truckers helping a family in need on the road, like changing a flat tire for a stranded family or delivering essential supplies to a rural family during tough times.